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Full text of "Zirconium and its compounds"

ZIRCONIUM 

AND ITS 

COMPOUNDS 



BY 

FRANCIS P. VENABLE 




American Chemical Society 
Monograph Series 



BOOK DEPARTMENT 
The CHEMICAL CATALOG COMPANY, Inc. 

ONE MADISON AVENUE, NEW YORK, U. S. A. 
1922 



27V ^ 



)' 13025f; BY* 
The CHBMC^'CjA'pAfpG: COMPANY, Inc; 



Press of 

J. J. Little & Ives Company 
New York, U. S. A. 



GENERAL INTRODUCTION 

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3 



4 GENERAL INTRODUCTION 

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GENERAL INTRODUCTION 5 

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PREFACE 

I wish to express my obligations in the preparation of this book to 
the Index to the Literature of Zirconium by A. C. Langmuir and 
Charles Baskerville, and especially to the compendium given by R. 
Jacoby in Gmelin-Kraut's Handbuch der anorganischen Chemie. 

I have not sought to record every observation or detail given in the 
literature, many of which are faulty or erroneous, but only such as 
seemed to have an essential bearing on the subject. My purpose has 
been to give a systematic, clear, and sufficiently full account of the 
chemistry of zirconium which should prove useful in connection with 
the increasing interest attaching to this element. 

This book is affectionately inscribed to my daughter, Louise M. 
Venable, and to my son, Charles S. Venable, both of whom have ren- 
dered invaluable aid in its preparation. 



FRANCIS P. VENABLE 



University of North Carolina 
June, 1921 



CONTENTS 



PAGE 

CHAPTER I. HISTORY AND OCCURRENCE 15 

CHAPTER JI. ZIRCONIUM AND ITS PROPERTIES .... 22 

Preparation. Specific Gravity. Thermal. Electrical. 
Chemical. 

CHAPTER III. COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 34 

With Hydrogen. With Oxygen. With Hydrogen and Oxy- 
gen. Higher Oxides. With Nitrogen. With Carbon. 
With Sulphur. With Boron. With Silicon. With Phos- 
phorus. 

CHAPTER IV. COMPOUNDS OF ZIRCONIUM WITH THE HALOGENS 

AND THEIR ACIDS 53 

With Fluorine. With Chlorine. With Bromine. With 
Iodine. 

CHAPTER V. COMPOUNDS WITH THE ACIDS OF SULPHUR AND 

SELENIUM 76 

With Sulphurous Acid. With Thiosulphuric Acid. With 
Sulphuric Acid. With Selenious Acid. With Selenic Acid. 

CHAPTER VI. COMPOUNDS WITH ACIDS OF THE NITROGEN GROUP 

AND RARE INORGANIC ACIDS 87 

With Nitric Acid. With Acids of Phosphorus. With Acids 
of Arsenic. With Acids of Antimony. With Chromic Acid. 
With Tungstic Acid. With Molybdic Acid. With Va- 
nadic Acid. 

CHAPTER VII. COMPOUNDS WITH ACIDS OF THE SILICON GROUP 97 
With Titanic Acid. With the Silicic Acid. 

CHAPTER VIII. ZIRCONIC ACID AND THE ZIRCONATES . . . 

Zirconic Acid. The Zirconates. 

9 



10 CONTENTS 

PAGK 

CHAPTER IX. COMPOUNDS WITH ORGANIC ACIDS AND RADICALS 110 

With Carbonic Acid. With Formic Acid. With Acetic 
Acid. With Citric Acid. With Oxalic Acid. With Tar- 
taric Acid. With Benzoic Acid. With Salicylic Acid. 
With the Cyanogen Acids. Zirconium Tetrahalides with 
Organic Bases and Radicals. 

CHAPTER X. ANALYTICAL METHODS 120 

Qualitative. Quantitative. Separation from other Ele- 
ments. 

CHAPTER XI. TECHNICAL APPLICATIONS OF ZIRCONIUM AND ITS 

COMPOUNDS 126 

Precious Stones. Oxy-hydrogen Light. Gas Mantles. 
Incandescent Filaments. Alloys. Furnace Applications. 
Refractories. Enamels. Glass. Textile Applications. 
Colloidal Applications. Medicinal Use. Abrasive. Chlo- 
rinating Agent. 

CHAPTER XII. PATENTS 133 

BIBLIOGRAPHY 149 

INDEX 171 



ZIRCONIUM 
AND ITS COMPOUNDS 

Chapter I 
History 

While this element is widely distributed, and fairly abundant, its 
similarity in general properties to other so-called earths, especially 
alumina, the difficulty of separation from them, and the absence of 
any easy characteristic test caused it to escape the notice of the 
earlier chemists. It is a mark of the careful analytical work done 
by Klaproth (392) that he should have discovered it and announced 
its existence conclusively in 1789. In that year he reported that in 
analyzing the jargon of Ceylon he had obtained 31.5 p.c. silica, 0.5 p. c. 
iron and nickel oxides, and 68 p.c. of an earth differing essentially 
from all known to him. This he called Zirkonerde. A few years later 
Klaproth (393) analyzed also the hyacinth of France and found the 
same new earth. In 1797 Guyton de Morveau (274) published his 
analyses of zircons from various localities, confirming the work of 
Klaproth. About the same time Vauquelin (726) examined this 
new earth, to which the name zirconia was given, and detailed the 
preparation and properties of some of its compounds. In 1798 
Trommsdorff (711) applied all of the methods then known for the 
decomposition of this earth but without success, and it was not until 
1824 that Berzelius (50) found a method for its decomposition and 
for the preparation of the element zirconium, though in an impure 
form. Two years later (53) Berzelius determined its atomic weight. 

At various times announcements have been made as to the com- 
plexity of zirconium or its being accompanied by some hitherto un- 
known element. This is not surprising when one considers the large 
number of other elements which have been recognized as present in 
zircons, the prolonged operations necessary for complete separations, 
and the ease with which zirconium forms basic compounds of varying 

15 



16 tl ZIHQpNIUM AND ITS COMPOUNDS 

dontent and^widel/ differing solubilities. In 1845, Svanberg (692) 
claimed that in decomposing zircons he had come across another earth 
which differed from zirconia in the solubility of its chloride, of the 
double sulphate with potassium and of its oxalate, and which also 
had a lower atomic weight. This earth he called noria and the sup- 
posed new element norium. In 1853 Sjogren (659) believed that he 
had found this noria in the mineral catapleiite. According to his 
determinations its density was 5.5 while that of zirconia was 4.3. The 
existence of noria was satisfactorily disproved by the works of Ber- 
lin (43), Hermann (325), Marignac (468), and Knop (400). 

In 1864 Nylander (529) reported the existence of two earths in 
zirconia, an observation which has not been confirmed. In 1869 
Sorby (667) announced that in the Ceylon jargon he had discovered 
a new element with a peculiar absorption spectrum to which he gave 
the name jargonium, but later (668, 669)' found he had fallen into 
error through the presence of a small amount of uranium, which is 
commonly present in zircons wherever found. In the same year 
Church (141) drew the conclusion from his spectroscopic examination 
that zirconium was accompanied by a new element to which he gave 
the name nigrium. Here again is an illustration of the ease with 
which a mistake can occur from accompanying impurities, such as 
thorium, yttria, and the rare earths which are found in the zirconium 
minerals coming from many different sources. 

The announcement by Hofmann and Prandtl (347) that about 
one-half of the zirconia obtained from euxenite from Brevig con- 
sisted of a new oxide which they called euxenerde and which had a 
considerably higher atomic weight has not been confirmed by further 
investigation. Hauser and Wirth (301, 302) working with twelve 
different minerals secured from widely separated localities failed to 
get the characteristic reactions reported for euxenerde. Furthermore 
the zirconia was separated by the usual methods and each sample 
purified by fractionation and the fractions examined spectroscopically 
with the result that there was no decomposition of the zirconium nor 
separation of a companion element, only those already known being 
identified. 

Occurrence 

While zirconium can not be ranked among the abundant elements 
in nature it is widely distributed and found in a number of localities 
in workable quantities. Since no delicate and characteristic test is 



HISTORY 17 

known for it, its presence has failed of detection in many minerals. 
Traces are easily lost sight of when it accompanies titanium, alu- 
minum, and the rare earths in small amount. 

Zirconium is found in crystalline rocks (especially in granular 
limestone) in chloritic and other schists, in gneiss, syenite, granite, 
and beds of iron ore. The syenitic rock called "zircon syenite" con- 
tains crystals of zircon along with epidote, clseolite, oligoclase, and 
gegirine. It is found also in pegmatite, sandstone, ferruginous sands, 
and in a number of minerals in which it is present only in small 
amounts or traces. So constant is its presence in the older igneous 
rock that Strutt (688, 689) has made use of its uranium-lead ratio 
as a means of calculating their relative age. Crystals of zircons are 
common in auriferous sands and are found in volcanic rocks. 

The most widely distributed and abundant mineral containing 
zirconium is the silicate, known in the common form as zircon. From 
this the name of the element is derived. It has a hardness of 7.5 
and a density varying from about 4.0 to 4.7, averaging about 4.65. 
As a normal silicate its theoretical composition would be ZrO 2 , 67.2 
p.c.; Si0 2 , 32.8. The percentage of zirconia varies, however, from 
61 to 66.8 p.c. The most common impurity is iron, but quantitative 
analyses (733) show traces of sodium, potassium, magnesium, cal- 
cium, aluminum, iron, lead, tin, uranium, erbium, and other elements, 
and Linnemann (449) found in addition zinc, copper, bismuth, man- 
ganese, cobalt, and nickel. The presence of some of these is doubtless 
due to infiltrations in the cracks of the crystals from the surround- 
ing soil. 

There are references to zircons in very early times. On account 
of its hardness it was used as a material from which to cut cameos 
and engraved signets. Intaglii of zircons are not at all uncommon 
among ancient gems. Under the name of the jacinth it is mentioned 
by Agricola and Interpe. It is mentioned also in the Book of Revela- 
tion. The jacinth seems to have been the colorless or yellowish 
variety. Brownish, orange, or reddish varieties were known as hya- 
cinths and sometimes confused with topazes and garnets. There 
would seem to be little reason, however, for the substitution for jacinth 
in the revised version of Revelation. The Ceylonese called it jargon 
and the colorless or slightly smoky varieties were sold as inferior 
diamonds. While resembling the diamond in lustre, they were less 
brilliant and not so hard and were comparatively worthless. De Lisle 
in 1783 writes of the Diamant Brut or Jargon de Ceylan. One singu- 



18 ZIRCONIUM AND ITS COMPOUNDS 

lar use is mentioned by Fourcroy, who says, "The hyacinth from Ex- 
pailly (near Le Puy) in France was formerly placed in collections of 
the materia medica to be used in some pharmaceutic compositions." 

The zircons of Ceylon are mainly found in alluvial sands. Those 
of the Ural Mountains are chiefly in the gold regions. They are also 
found in Greenland, Norway, Transylvania, Bohemia, the Tyrol, 
France, Italy, Australia, New Zealand, etc. In the United States the 
zircon is commonly associated with magnetite sand or ore, and it has 
been found in a number of states, including North Carolina, South 
Carolina, Tennessee, Oklahoma, Florida, New York, New Jersey, 
Pennsylvania, California, Virginia, and others. By microscopic ex- 
amination of the rocks this list can be greatly extended. Its com- 
mercial occurrence is chiefly in masses of pegmatite and pegmatized 
gneisses, and in these it is often in fairly large crystals, weighing up 
to fifteen pounds. So far only three localities in the United States 
are known where it occurs in sufficient quantities for mining. These 
are on Green River in Henderson County, North Carolina, at Ander- 
son, South Carolina, and near Ashland, Virginia. Shipments have 
been made from the first-named locality amounting to about 20,000 
pounds since 1902 and perhaps 60,000 pounds prior to that date. 
Very large crystals weighing as much as fifteen pounds have been 
found at Renfrew, Canada, but the supply seems to be limited. 
Opaque green zircons have been found in St. Lawrence County, New 
York, and black ones in New Jersey. Small but very beautiful crys- 
tals, some of them deep emerald green, are found near Pike's Peak, 
Colorado. In the volcanic tufa of Vesuvius it is found in small white 
and blue octahedra. 

The zircons of Ceylon occur mainly in alluvial sands. The amount 
in the gold regions of the Ural Mountains is said to be large. There 
appear to be considerable deposits in Greenland and Norway and also 
in New South Wales. 

Microscopic crystals are widely distributed in the sedimentary 
rocks, the material having been largely derived from the older rocks, 
e.g., in the variegated sandstones of the Black Forest, in carboniferous 
limestones, and in the sands of the valley of the Main. Thiirach has 
shown that microscopic zircon is rarely absent from archsean and 
sedimentary rocks. It also occurs in many igneous rocks and is 
widely distributed in basalts and dolerites. Its resistance to weath- 
ering and attrition causes the zircon to be found in many auriferous, 
volcanic, and shore sands. The researches of the United States Geo- 



HISTORY 19 

logical Survey upon the black sands would tend to show its universal 
presence in granite and allied rocks. 

In color the crystals vary from colorless through a number of colors 
as amber, smoky, red, reddish-brown, blue, green, black to a dull 
opaque brown. The small white and blue octahedra of Vesuvius 
have been mentioned. The finest gem stones come from Ceylon, 
Mudger, and New South Wales. 

Meyer (485) has given the following description of the occurrence 
and mining of the native zirconia ore in Brazil. The deposits are in 
the Caldas region which lies partly in the State of Minas Geraes and 
partly in the State of Sao Paulo, approximately 130 miles north of 
the city of Sao Paulo. It is a mountainous plateau, the main eleva- 
tion of which is about 3600 feet. The surface is undulating, present- 
ing differences in level of from 300 to 600 feet. The whole area is 
bounded on all sides by ridges rising abruptly from 600 to 1200 feet 
above the general level and forming a roughly elliptical inclosure 
with a major axis of approximately 20 miles in length and a minor 
axis of 15 miles. The predominant rock of the plateau is phonolite. 

The ore can be divided roughly into two classes. First, alluvial 
pebbles ranging in size from one-half inch to three inches in diameter, 
generally carrying about 90-93 p.c. of zirconia. The pebbles, known 
as "favas" and having a density of 4.8-5.2, are found along small 
stream beds and on the talus slopes of low ridges. Second, zirconia 
ore proper or zirkite, which ranges in shade from a light gray to a 
blue-black, the lighter colored material carrying a larger percentage 
of zirconium silicates and showing a minimum content of 73 p.c. zir- 
conia. The blue-black ore generally carries 80-85 p.c. of zirconia. 

Prior to the investigations of Derby and Lee (177) this zirkelite 
was considered identical with baddeleyite. It has now been shown 
that it is a mechanical mixture of three minerals, namely, brazilite, 
zircon, and a new and unnamed zirconium silicate carrying about 75 
p.c. of zirconia. This new mineral has the same crystal form as zircon 
but is readily soluble in hydrofluoric acid, while zircon is practically 
not attacked. 

Several large outcrops of the ore occur on the extreme westerly 
edge of the plateau, one or two boulders weighing as much as 30 tons. 
Owing to the hardness of the ore it is almost impossible to drill holes 
for explosives, and in handling large masses it is found necessary to 
resort to the primitive method of heating the rock and suddenly cool- 
ing with water. In some of the deposits the ore occurs in the form 



20 ZIRCONIUM AND ITS COMPOUNDS 

of gravel and large pebbles embedded in a reddish clay. On drying 
the ore can be separated by screening. It is washed thoroughly clean 
from ferruginous matter before shipping. Transportation of the ore 
to the nearest railroad is difficult. From surface indications the de- 
posits are of vast extent. The shipment of this ore reached in 1913 
a total of 1,119 tons. The maximum production of ore in the United 
States (practically all from North Carolina) was reached in 1905 
with a yield of 4 tons. 

It is evident that the most important commercial source of zir- 
conium is the native zirconia of Brazil whose occurrence has been 
described. This Brazilian ore is reasonably pure and may be used 
direct in refractories as zirconia or can be easily converted into the 
desired compounds, which is much more difficult in the case of zir- 
cons. Baddeleyite is the mineralogical name, and distinct fibrous 
bbtyroidal, or columnar crystals of this mineral are found in the ore, 
which is known as brazilite. Jacupirangite is a variety of baddeley- 
ite also crystalline. Besides the occurrence of baddeleyite in Brazil 
it has been found in the United States, Ceylon, Sweden, and Italy. 
The commercial ore is often called zirkite and has some zircon mixed 
with it. Zirkelite is also present and is a variety of zirconium silicate 
containing about 50 p.c. of zirconia. 

Zirconium has been reported (317, 478) as present in certain 
spring waters and its presence has been detected (615) in the solar 
spectrum. It has also been reported as having been found in a 
meteorite, but the identification seems to have been incomplete. 

LIST OF ZIRCONIUM MINERALS. 

Adelfolith or p.c.ZrO 2 

malacone weathered zircon 47.42 

Alvite weathered zircon 39-3248 

Anderbergite R 3 V 2 Zr 9 (SiO 2 ) 12 .18 H 2 O ' 41.2 

Arrhenite hydrated silicotitanate of Zr, Fe, Ce, Er 342 

Astrophyllite (SiTiZr) 5 O lfl (MnFe)4(KNaH)4 4.97 

Auerbachite weathered zircon 55.18 

Baddeleyite native zirconia up to 99^0 

Beccarite zircon containing Ca and Fe 62.16 

Brazilite see baddeleyite 800 

Catapleiite H 2 (Na 2 Ca)ZrSi 3 Ou 30.-40' 

Chalkolamprite a niobate-silicate of Zr ' 57 

Cyrtolite weathered zircon 36-61 

Elpidite Na 2 Si 2 5 .Zr(Si 2 5 ) 2 ' 20^ 

Erdmannite basic silicate of cerium earths and ZrO 2 varying 

Eudialyte Na 1 3(CaFe) 6 (SiZr) 2 oO S2 Cl 10-20 

Fergusomte niobate (tantalate) Yt, Ce, U, Th, etc, up to 7. 

Hiortdahhte zircon pyroxene 21 5 

Kochelite niobate of yttria earths 



HISTORY 21 

LIST OF ZIRCONIUM MINERALS. 



p.c. 

Lovenite (SiO 3 ) 2 MnCaFe.(ZrOF)Na 30. 

Mosandrite Zr, Th, Ce, Ti silicate 7.4 

Oliveiraite 3ZrO 2 .2TiO 2 .2H 2 O 63.36 

Orvillite 8ZrO 2 . 6SiO 2 . 5H 2 O 71.88 

Polymignite metazirconotitanate and tantaloniobate 14.-30. 

Pyrchlor niobate-titanate 

Rosenbuschite zircon pyroxene 20. 

Tachyaphaltite weathered zircon 39. 

Tantalite a tantalate (niobate) up to 11. 

Uhligite (ZrTi)O 5 .Ca.(TiAl)O 5 Al 22. 

Wohlerite Si M Zr 3 Naa04 S F, . Ca 10 Na 5 15.-23. 

Zirkelite zirconium silicate 50. 

In the following minerals zirconium is found in small amounts: 
Auerodite, bragite, cerite, columbite, edwardsite, eucrasite, hypers- 
thenite, johnstrupite, leukosphenite, karyocerite, knopite, koppite, 
mackintoshite, melanocerite, monazite, niobate, nohlite, samarskite, 
seybertite, sillimanite, sipylite, tritonite, tschefifkinite, tyrite, uhligite, 
uraninite, vietinghoflSte, xeontime, yttergranate, and zoisite. 

The zirconium minerals have been classified under the following 
types: 

1. Zircon type. Adelfolith, alvite, anderbergite, arrhenite, auer- 
bachite, benarite, engelhardite, erdmannite, hiortdahlite, ilmenite, 
malacone, mosandrite, oerstedtite, ostranite, pyrobuschite, tachya- 
phaltite, zircon. 

2. Add type. Astrophyllite (SiTiZr) 5 16 (MnFe) 4 (KNaH 4 ) 
and elpidite Si 4 Zr0 10 .Na 2 eudialite, fergusonite, catapleiite, leuko- 
sphenite, lovenite, polymignite, wohlerite. 

3. Oxide type. Baddeleyite, brazilite, zirkelite. 

4. Tantalate type. Bragite, chalkolamprite, pyrochlor, tantalite. 



Chapter II 

Zirconium and its Properties 
Preparation .of Zirconium 

The preparation of metallic zirconium presents many difficulties 
and numerous .attempts during nearly a century failed to produce the 
metal reasonably free from impurities. Some of the chief obstacles 
arise from its strong affinity for oxygen, and hence the difficulty of 
reducing the oxide and the ease with which the metal is reoxidized 
at high temperatures; also the readiness with which it absorbs and 
combines with hydrogen, nitrogen, boron, and silicon, and its tendency 
to form alloys with the light metals such as aluminum and mag- 
nesium. 

It was along the line of the reduction of the oxide that the first 
efforts to produce the metal were made and failed. These were by 
Trommsdorff (711) in 1798 and Davy (170) in 1808. Attempts at 
reducing zirconia in a stream of hydrogen failed and it is now known 
that even had they succeeded the hydride would have been formed 
if the temperature had not exceeded 800. Nor can the tetrachloride 
be reduced by hydrogen at a temperature under 600. 

In 1824 Berzelius (50) first prepared the metal by the reduction 
of the double fluoride of zirconium and potassium by means of potas- 
sium. 

2KF . ZrF 4 + K = 6KF + Zr. 

The dried and finely powdered double fluoride was heated in layers 
of potassium in a small iron cylinder closed at one end, and placed 
in a platinum crucible, covered with a top. This mixture was stirred 
with an iron wire and heated over a lamp, first gently and then to 
low red heat. In this way the reduction went on quietly. On treat- 
ing the cooled mass with water a little hydrogen was evolved and 
amorphous zirconium separated. This contained some zirconia. It 
was further washed with water, digested for six hours at 40-50 
with equal parts of hydrochloric acid and water, then washed on a 

22 



ZIRCONIUM AND ITS PROPERTIES 23 

filter with a solution of ammonium chloride, and lastly with alcohol. 
The product was impure and observations made upon it as to the 
characteristics of elementary zirconium were consequently inaccurate. 
Subsequent experiments seem to show that the double fluoride is the 
best source-material for the preparation of the metal, a tribute to 
the knowledge and skill of Berzelius, but many modifications in the 
method as outlined above have been gradually introduced. Franz 
(230) found the double fluoride 3KF.ZrF 4 , prepared as minute crys- 
tals by precipitation with an excess of potassium fluoride, to be pref- 
erable to 2KF.ZrF 4 but used aluminum as a reducing agent, heating 
the mixture in a graphite crucible. He obtained an alloy of zir- 
conium, however, containing 1.03 p.c. of aluminum and 0.17 p.c. of 
silicon. The temperature was kept high to lower the contents of 
aluminum. Troost (713, 714) repeating the experiment of Berzelius, 
obtained the same amorphous zirconium mixed with zirconia. His 
reduction by means of aluminum yielded crystals in the form of 
oblique prisms which were separated by means of dilute hydrochloric 
acid and revealed on analysis the presence of both aluminum and 
silicon. They showed an easy cleavage and had a density of 4.15, 
were more fusible than silicon, and resisted the action of oxygen at 
red heat. At white heat a coating of oxide was formed. They com- 
bined with chlorine with incandescence and, at fusion temperatures, 
decomposed caustic alkalies with the evolution of hydrogen. They 
were slightly soluble in hot sulphuric acid and easily dissolved by 
aqua regia and hydrofluoric acid. 

Wedekind (776) attempted the reduction of the double fluoride 
with aluminum, obtaining different products according to the method 
of procedure, which on analysis indicated various alloys with alu- 
minum, namely, ZrAl 2 , Zr 3 Al 4 , ZrAl 3 . 

He also (785) repeated the method of Berzelius with precautions 
to prevent oxidation. Sodium was found to be preferable to potas- 
sium as the reducing agent. The product was dried at 200 in vacuo, 
leaving a hygroscopic preparation. This was further heated to 300 
in vacuo, becoming then pyrophoric, catching on fire on exposure to 
air fourteen hours after cooling. The product obtained by Berzelius, 
he concluded, was a mixture of very finely divided metal and zirconia. 
Some investigators had suggested that the oxide formed was a sub- 
oxide. Wedekind's conclusions, however, were against this. The ex- 
istence of this oxide, ZrO, has been maintained by Winkler (817) and 
Dennis and Spencer (176). The metal in very fine subdivision seems 



24 ZIRCONIUM AND ITS COMPOUNDS 

to be very susceptible to the action of oxygen, nitrogen, etc., probably 
on account of the large surface exposed. 

A zirconium said to be of great purity was prepared by Weiss and 
Naumann (806). They made use of the Berzelian method, substitut- 
ing sodium for potassium and further purifying the product. Also 
commercial zirconium was bought from dealers and purified as fol- 
lows: The impure metal was pressed into pencils and used as the 
electrodes in a bomb which had been exhausted of air, then filled 
with hydrogen and this also pumped out. After several repetitions 
the hydrogen was reduced to a pressure of 10-11 mm. and the electric 
current turned on. The zirconium pencils were kept at a distance of 
2-3 mm. The current used was one of 60-70 amperes at 20-25 volts. 
The metal of the positive electrode melted and fell in drops upon the 
negative electrode which was placed underneath. The metal collected 
in various experiments was found to range from 99.76 p.c. to 99.89 p.c. 
pure. When ammonia under diminished pressure was substituted for 
hydrogen, metal ranging from 99.69 p.c. to 99.81 p.c. pure was ob- 
tained, showing that at this temperature zirconium apparently does 
not react with either hydrogen or nitrogen. 

Attempts to reduce zirconia by means of magnesium were made 
by Phipson (547) and by Bailey (19). The resulting product re- 
tained oxide. Also Wedekind (776) prepared amorphous zirconium 
by heating thin pencils of the double fluoride with magnesium in an 
electric furnace with a current of 90-100 amperes. This gave a dark, 
somewhat metallic-like mass containing 94.12 p.c. of zirconium. A 
later experiment (787) yielded a compact metal with 96.55 p.c. zir- 
conium and 4.14 p.c. oxygen. Warren (761) states that zirconium can 
be reduced from solutions of its salts by the replacement action of 
magnesium. Wedekind (777) heating zirconia in a nickel crucible 
with 40 p.c. over the theoretical quantity of magnesium obtained a 
colloidal zirconium (purity not determined) which was deep blue 
in reflected light. On the passage of an electric current the particles 
migrated with the positive stream, which is opposite to the observa- 
tion of Whitney (814). 

Tucker and Moody (723), who tried the reduction of zirconia by 
the Goldschmidt method, were unsuccessful. Attempts by Wede- 
kind (773) to reduce zirconia by means of boron yielded the boride. 
When carbon was used the carbide was formed. Moissan (500) in 
an electric furnace with a current of 360 amperes and 70 volts 
brought powdered zircons to fusion and boiling with the giving off 



ZIRCONIUM AND ITS PROPERTIES 25 

of white fumes. He states that in a carbon crucible he obtained 
metal containing neither carbon nor nitrogen. On mixing the zircons 
with an excess of carbon a carbide was formed having 4.22-5.10 p.c. 
of carbon. This product gradually decomposed in the air. By fusing 
together the zirconium carbide and zirconium thus prepared he ob- 
tained metallic zirconium. The metal was very hard, scratching 
glass and rubies and having a density of 4.25. The pure metal, how- 
ever, shows a wide variation from these properties, so Moissan was 
probably in error as to the purity of his preparatoin. 

Wedekind (785) found it possible to reduce zirconia by means of 
calcium: 

Zr0 2 + Ca 2 = Zr + 2CaO. 

Commercial calcium was used (91.8-94.9 p.c. Ca.). The impurities 
were iron, silicon, and chlorine. The mixture was placed in an iron 
tube which was then exhausted to 0.5-0.1 mm. pressure. This was 
heated until the reaction set in and then the reaction moderated by 
cooling. The porous, baked mass was withdrawn, w r ashed with water, 
alcohol, dilute hydrochloric acid, and finally acetone, dried, and 
heated in vacuo. On polishing it gave a fine metallic mirror. Anal- 
ysis showed 97.7 p.c. zirconium, the remainder being zirconia. It was 
samples of this preparation which were sent to Burgess and v. Bolt on 
for the determination of the melting point. The density was found 
to be 6.2. Sander (633) has patented a method for preparing zir- 
conium by heating in vacuo the hydride or nitride under the con- 
tinuous withdrawal of the gases formed. 

Lely and Hamburger (440) have prepared a very pure zirconium 
by heating zirconium tetrachloride and sodium in a bomb with an 
electric current. The metal was obtained in lamina? which could be 
pressed into rods. It was very ductile and gave a mirrorlike surface 
on burnishing. It was easily oxidized on heating, dissolved in cold 
hydrofluoric acid, concentrated or dilute, and in concentrated hot 
sulphuric acid, also in hot aqua regia. The analysis given, namely, 
0.2154 grams of metal yielding 0.2915 grams of zirconia, would prove 
it to be exactly 100 p.c. pure if the atomic weight is taken as 90.6. 

Becquerel (35) was the first to attempt the preparation of the 
metal by electrolysis. Very concentrated solutions of the chloride 
were subjected to the action of the voltaic pile. The metal was gotten 
in the form of a black, amorphous powder which was acted upon by 
air. Troost (714) by the electrolysis of the melted double fluoride 



26 ZIRCONIUM AND ITS COMPOUNDS 

obtained lustrous crystalline laminae which decomposed cold water. 
Wedekind (774) on repeating this experiment obtained only impure, 
amorphous zirconium as a gray-black, easily oxidized powder. 

Colloidal zirconium. Several of the methods for preparing zir- 
conium yield part of it in such finely divided form that it is appar- 
ently in the colloidal form. Thus Wedekind (774, 780, 782) reported 
that when the double potassium and zirconium fluoride is reduced by 
potassium, the excess of potassium removed by alcohol and the potas- 
sium fluoride by washing with water and a solution of potassium 
nitrate, part of the zirconium in the final washing with water passes 
through the filter. When this is subjected to dialysis the hydrosol 
in transmitted light is gray-black in color and in reflected light an 
opalescent black. It shows a relatively high stability to acid elec- 
trolytes while alkaline electrolytes coagulate it. The hydrogel sepa- 
rates in black flocks. Neutral electrolytes cause no direct coagula- 
tion. A white precipitate which is redissolved on shaking may be 
formed. Hydrochloric acid precipitates it on prolonged boiling. Hy- 
drogen dioxide causes immediate precipitation. 

Again (777, 814), when zirconia is reduced by an excess of mag- 
nesium ground with water, treated with warm, concentrated ammo- 
nium chloride solution and then warm, dilute hydrochloric' acid part of 
the solid goes through a filter, giving a colloidal solution which is deep 
blue in transmitted light. The particles migrate with the positive 
stream towards the cathode. This latter observation is opposed to 
that of Whitney (814), who found the supposed colloidal zirconium 
under the influence of the electric potential to migrate in the direction 
of the negative stream. This colloidal matter may have been con- 
taminated with the nitride, hydride, or with some partially oxidized 
metal. A colloidal solution of a similar blue-black color has been 
prepared from unreduced zirconia. 

Properties of Zirconium 

So far as zirconium has been prepared in a condition of reason- 
able purity it seems to be known only as an amorphous black powder, 
which when melted is steel-gray and on burnishing gives a lustrous 
metallic mirror. The existence of a crystalline and a graphitic form 
has at least not been established. Investigators who have reported 
them had alloys rather than the pure metal in hand. It is natural 
that in earlier times their existence should have been surmised from 



ZIRCONIUM AND ITS PROPERTIES 27 

the analogy of its congener, carbon. The element has been prepared 
in a colloidal form, though some doubt exists as to its elementary 
condition in this form. Its degree of hardness has not been satis- 
factorily determined. The data of Moissan, namely, 4.7, and power 
to scratch rubies are evidently to be referred to the carbide or mix- 
ture of metal and carbide. Marden and Rich (467) gave the hard- 
ness as 6.7. 

Specific Gravity. Many of the determinations of the density are 
quite unreliable on account of impurities in the samples taken. Such, 
for instance, are the figures given by Troost (713), 4.15; by Meyer 
(489), 4.08; by Moissan (500), 4.25. Wedekind (785) out of a series 
of determinations on metal over 99.5 p.c. pure preferred the figures 
6.29. Weiss and Naumann (806), using also very pure metal (99.8 
p.c.), reported the density as 6.4. The close accord of the two last 
observers would lead to the conclusion that 6.4 is to be taken as the 
density of the pure metal. The atomic volume then is 14.16 (At.wt. 
90.6). 

Melting Point. The discrepancies in the few determinations which 
have been made of this constant are serious and now that the metal 
can be prepared in purity a careful redetermination is demanded. 
Supposedly pure metal was furnished by Wedekind to both v. Bolton 
and Burgess. The former (89) , using a vacuum furnace and Siemens 
and Halske optical pyrometers, which had a probable error of 50 
at the temperature used, gave as the results of two experiments 2330 
and 2380 or an approximate mean of 2350. This is near the melt- 
ing point of zirconia. Burgess (113) used a platinum support so that 
the possible formation of an alloy was not eliminated. Still the 
method was tested with iron, chromium, cobalt, nickel, and man- 
ganese, where the same possible source of error existed, and results 
were obtained in accord with the known melting points of these metals. 
His three experiments with zirconium gave 1529, 1533, 1523, and 
he adopted the figure 1530 for the melting point. Marden and Rich 
(467) gave the melting point as a little over 1600. Guertlar and 
Pirani (270) give a probable melting point of 1700. 

Specific Heat. The earliest determination of the specific heat 
was made by Mixter and Dana (499). The figure obtained was 
0.0667 at 99.7. This would give an atomic heat of 6.07. The speci- 
men of zirconium contained silicon and probably other impurities. 
Wedekind and Lewis (786) found the specific heat to be 0.06725, 
which would give an atomic heat of 6.1. Later determinations by 



28 ZIRCONIUM AND ITS COMPOUNDS 

Wedekind (785) gave the range for different samples as 0.0656 to 
0.0735, or an atomic heat of 6.19 to 6.66. Weiss and Naumann (806) 
with a very pure specimen obtained the high result of 0.0804, or an 
atomic heat of 7.31. The latter, if confirmed, would assign to zir- 
conium the highest atomic heat known. All these determinations 
were apparently made at the range 0-100. Dewar (186) has deter- 
mined the specific heat at temperatures between that of liquid nitro- 
gen and liquid hydrogen, finding it to be 0.0262, which gives an atomic 
heat of 2.38 at that range. 

Electrical Properties. Meyer (489), making use of commercial 
specimens, found zirconium to be diamagnetic and with an atomic 
magnetism k = 0.0114 X 10' 6 at 17. Pure amorphous zirconium is 
a conductor of electricity. When pressed into pencils it can be used 
as electrodes for the arc. For filaments, rhodium has sometimes been 
added. Bohm (83) has recorded a number of observations as to the 
conductivity of zirconium filaments. Owen (533) has examined the 
thermomagnetic properties of zirconium, determining the specific sus- 
ceptibility which is equal to the field intensity divided by the density. 
The determinations were made on "crystallized zirconium." 

Optical Properties. Karl (382) has reported his experiments upon 
the triboluminescence of zirconium in compounds. Gladstone (245) 
found the specific refraction of zirconium to be 0.242 and the atomic 
refraction 21.9. 

Spectrum. The earliest examination of the spark spectrum of 
zirconium was made in 1869 by Thalen (701). This was in the visible 
spectrum and twenty-six lines are recorded with their intensity on the 
old scale. They are as follows: 

I i I i 

Orange 6343.5 3 Indigo 4497.5 4 

6310.0 3 " 4494.5 4 

6140.5 1 " 4443.0 4 

6132.5 3 " 4380.0 4 

6127.0 1 " 4370.0 4 

Yellow 5384.5 4 " 4360.0 4 

5349.5 3 " 4242.0 4 

Green 5190.5 3 " 4241.5 4 

4815.0 1 Violet 4228.5 4 

4771.0 1 " 4209.5 4 

4738.5 1 " 4209.0 4 

4709.5 1 " 4155.0 2 

4686.5 1 4149.0 2 

The spectrum of zirconium is especially rich in ultra-violet lines. 
Exner and Haschek (214) have measured 1424 of these lines. The 



ZIRCONIUM AND ITS PROPERTIES 29 

zirconium used was prepared by the Moissan method and hence prob- 
ably contained carbon and other impurities. The chief lines and 
their intensity (Rowland's scale) are given by Gmelin and Kraut. 1 

I i I i 

3392.20 20 3958.39 20 

3438.39 20 3991.31 20 

3496.40 20 3999.18 20 
3556.89 20 4149.43 20 

3698.41 20 4209.21 20 
3751.85 20 4380.12 20 
3836.98 20 

The arc spectrum, according to Rowland and Harrison (616) , gives 
820 lines, of which the chief are the following: 

I i I i 

3392.14 10 4227.94 10 

3496.38 10 4239.49 10 

3890.49 10 4282.36 10 

3891.53 10 4507.32 10 

3929.71 10 4535.90 10 

3973.63 10 4575.69 10 

4081.40 10 4688.00 10 

Vehle (731) has measured the arc spectrum in terms of the interna- 
tional normal. As a means of spectroscopic detection de Gramont 

(253) has recommended the use of the five lines in the blue between 
481.6 and 469, especially 474.0. 

The measurement of the ultimate rays of greatest photographic 
sensibility (international normal) has also been given by de Gramont 

(254) as follows: 

Rays 1/100 1/1000 5/10000 1/10000 5/100,000 

3698.16 + ? 

3572.47 + ? 

3505.66 -|- + 

3496.20 4- + -f- 

3438.23 

3391.98 + 4- 

3273.04 + 4- 

The decomposition of the zirconium lines into their components 
has been investigated by Moore (503) . The visible arc spectrum has 
also been mapped by Eder and Valenta (206) . They found it easiest 
to obtain by using the halides, as the oxy-compound gave a continuous 
spectrum from the glowing oxide. In the oxy-hydrogen flame the 
spectrum was also continuous. Eder (205) has also measured the 

1 Gmelin and Kraut. Handbuch der anorg. Chem. Bd. VI, p. 7. 



30 ZIRCONIUM AND ITS COMPOUNDS 

lines in the red and infra-red. Du Bois (86) has studied the selective 
absorption and the Zeeman effect. Moseley (506) has recorded the 
high-frequency spectrum. 

Chemical Conduct. 1. Towards other elements. According to 
Wedekind (785), amorphous zirconium when heated below 700 ab- 
sorbs hydrogen, combining with it to form a solid hydride which is 
fully dissociated at 800. It combines readily with oxygen, burning 
with brilliant light when heated considerably below red heat. The 
denser and much purer metal, however, was only slowly oxidized 
(789) when heated in air up to 270. Towards nitrogen amorphous 
zirconium shows a like readiness of combination, forming a nitride. 
The formation of this nitride is reported by several investigators 
when, in preparing the metal, the product was heated in the presence 
of air. At high temperatures (700-1000) zirconium does not com- 
bine with hydrogen or nitrogen, the temperature being above that for 
dissociation of the compounds. The oxide is stable at very high 
temperatures. When the metal is heated with carbon a carbide is 
formed, which if rich in carbon is gradually decomposed in air but 
otherwise seems stable. Zirconium readily combines at high tem- 
peratures with silicon and boron. With copper, silver, aluminum, and 
metals of the iron group and some other metals alloys are formed, but 
not with lead or tin (467) . Chlorine and bromine act upon zirconium 
when heated, forming the tetrahalides. Ammonia passed over heated 
zirconium gives the nitride. Sulphur also combines with the metal 
when heated. Red phosphorus gives a black powder. 

2. Behavior towards hydroxides and oxides. When heated with 
alkali hydroxides hydrogen is evolved, according to Troost (714), but 
this action takes place only so long as water is present. However, 
Wedekind reports solutions of alkali hydroxides to be without action 
(789). This discrepancy is doubtless due to the fact that Troost did 
not have as pure a metal. Fused with alkali hydroxides the action 
is only partial, with potassium nitrate it is explosive, and with copper 
oxide or lead oxide it is very energetic. Other oxides, as chromic, 
show no action up to 800 (789). Silica is reduced at a bright red 
heat (776). Boron trioxide and titanic oxide are also reduced. The 
great affinity of zirconium for oxygen has suggested its use as a reduc- 
ing agent and the use of its alloys as cleansing agents in metallurgical 
operations. 

Action of Acids. Hydrofluoric acid easily dissolves the metal in 
the cold, even the dilute acid acting upon it. Concentrated hydro- 



ZIRCONIUM AND ITS PROPERTIES 31 

chloric acid acts very slightly and nitric acid not at all. Hot con- 
centrated sulphuric acid acts energetically, giving off sulphur dioxide 
(789). Aqua regia also reacts readily. 

Position in the Periodic System. The position of zirconium in the 
periodic system was first settled by its analogies with the elements 
of the fourth group. In the first place, there is the formation of the 
typical oxide, Zr0 2 , and the occurrence of this free and combined with 
Si0 2 . Then there is the formation of the tetrahalides and the ready 
hydrolysis of the tetrachloride. From vapor density determinations 
of the tetrachloride, Deville and Troost (185) have shown the for- 
mula to be ZrCl 4 and hence the valence of zirconium four. Also the 
molecular weight determination of the acetylacetonate (69) gives the 
formula ZrR 4 . Furthermore, there is the amphoteric reaction of the 
hydroxide and the formation of zirconic acid, H 2 Zr0 3 , which is com- 
parable with H 4 C0 3 , H 2 Si0 3 , H 2 Ti0 3 , and H 2 Sn0 3 . These five ele- 
ments were grouped together by Mendeleeff in his first table arranged 
according to the atomic weights. By means of the high-frequency 
spectrum Moseley (506) and Friman (235) have determined the 
atomic number as 40, which confirms the above arrangement and set- 
tles the position of the element. 

Atomic Weight. Determinations of this constant for zirconium 
have been made by Berzelius (53), Hermann (319), Marignac (468), 
Weibull (794), Bailey (22), Venable (736), Venable and Bell~(744). 
A resume of these is given in the following table: 

No. Anr Atomic 

alyses Weight 

6 89.46 

7 89.54 

8 90.63 
5 90.79 
4 90.03 
4 91.54 

10 90.81 

1 88.64 

2 



Date 


Author 


Ratio 


1. 1826 


Berzelius 


Zr(SO<) 3 :ZrO, 


2. 1881 


Weibull 





3. 1889 


Bailey 


a 


4. 1881 


Weibull 


Zr(SeO.),:ZrO, 


5. 1860 


Marignac 


K.ZrFeiKaSO* 


6. 1860 


Marignac 


K 2 ZrF 8 :ZrO 2 


7. 1898 


Venable 


ZrOCl 2 .3H 2 O:ZrO 2 


8. 1844 


Hermann 


ZrCl 4 :? 


9. 1844 


Hermann 


2ZrOCl 2 :9H 2 O.ZrO 2 


10. 1917 


Venable 






and Bell 


ZrCU:4Ag 



13 91.76 



It is evident that the present uncertainty as to this fundamental 
constant leaves it in an unsatisfactory condition and more accurate 
determinations are necessary. The figure recommended by the Inter- 
national committee on Atomic Weights, which does not consider series 
10, is 90.6. 



32 ZIRCONIUM AND ITS COMPOUNDS 

Salts of Zirconium 

These fall into three classes. 1. Normal zirconium salts in which 
zirconium is the metallic cation with a valence of four. This is seen 
in the halides ZrF 4 and ZrCl 4 , also in combination with strong acids, 
Zr(So 4 ) 2 and Zr(N0 3 ) 4 . In the preparation of these water must 
be rigidly excluded on account of the ease of hydrolysis. The num- 
ber of these definitely known, outside of the binary compounds, is 
small and the existence of some reported is open to question. 

2. Zirconyl and basic zirconyl salts where the cation is the radical 
ZrO (118). These are the product of the hydrolysis of the normal 
salts and form the much larger number of the known compounds of 
this element. The tendency often is for more than one zirconyl radi- 
cal to enter into the combination. In some cases the increasing 
basicity seems to have no definite stopping point, as is indicated by 
the continuous dissolving of the hydroxide in solutions of the sul- 
phate or nitrate until a thick, gumlike product is obtained on reach- 
ing the limit of solubility. In the case of organic acids there are 
often formed basic salts whose composition depends upon the con- 
centration, the temperature, and the relative proportions of the con- 
stituents added. 

In the preparation of certain compounds by precipitation methods 
it has been found that the precipitate forms sometimes only after a 
considerable lapse of time or upon heating the solution. This is espe- 
cially the case where weak acids, such as the organic acids, are con- 
cerned. The compounds thus formed are found to be more or less 
highly basic zirconyl salts or mixtures of such. It seems reasonable 
to infer that the acid radical of the precipitant used forms only solu- 
ble compounds with the less hydrolyzed salts and insoluble ones with 
the more basic. It is possible also that in some cases these are not 
true chemical compounds but adsorption compounds in which the 
acid radical has been adsorbed by the colloidal hydroxide. Some of 
these products are distinctly gelatinous and can be washed and filtered 
with difficulty. On the other hand, some are granular and some dis- 
tinctly crystalline. The hypothesis of colloidal compounds is espe- 
cially probable wherever the acid radical can be practically removed 
or greatly reduced in amount by repeated washings of the precipitate, 
as is true with iodic acid and some organic acids. When, however, 
analysis reveals the same basic compound as being formed under 
varied conditions of dilution, etc., as is the case with the basic chro- 



ZIRCONIUM AND ITS PROPERTIES 33 

mate, it may be fairly assumed that a definite chemical compound 
has been formed. 

There has been little system in the assignment of formulas to 
the basic zirconyl compounds. Some have written them simply in 
the ratio of the zirconia to the acid anhydride, as 2Zr0 2 . S0 3 . Others 
report this basic zirconyl sulphate as ZrO 2 .ZrOS0 4 . Perhaps the 
most common formula is Zr 2 3 S0 4 . Such formulas fail to make clear 
the known facts. These substances are often gelatinous and, when 
hydrolysis is far advanced, the solutions become opalescent. On 
dialyzing the solutions leave zirconyl hydroxide as a hydrogel. Even 
the crystalline basic salts dialyze with difficulty and show partly col- 
loidal properties. They have been called half-colloids. Electrolytic 
dissociation shows often a migration of the zirconyl radical as an 
anion or a distribution of the zirconium between the anions and 
cations. It is well known that the migration of a colloid is largely 
influenced by the medium. Furthermore, there is practically always 
water of hydration or crystallization present. Considering these 
facts, it is suggested that the most suitable formula for these 
basic salts would have to include the zirconyl hydroxide. Thus 
Zr0 2 .ZrO.S0 4 becomes ZrO(OH) 2 .ZrOS0 4 and Zr 2 3 Cl 2 becomes 
ZrO(OH) 2 .ZrOCl 2 . This reveals at a glance the stepwise formation 

of the colloid and the liberation of the acid, e.g., ZrCl 4 + H 2 > 

ZrOCl 2 + 2HCl; 2ZrOCl 2 + 2H 2 O - -> ZrO(OH) 2 .ZrOCl 2 + 2HC1. 
Where several molecules of ZrOCl 2 are hydrolyzed at one step more 
complex products will result. This method of writing the formulas 
has therefore been adopted throughout this text wherever accurate 
knowledge of the composition of the substance was available. 

3. Zirconates. Zirconyl hydroxide ZrO(OH) 2 , which may be 
written H 2 Zr0 3 , here functions as an acid and is called zirconic acid. 
It combines with strong bases, giving zirconates as Na 2 Zr0 3 . CaZrO 3 , 
etc. 

Valence 

While zirconium is quadrivalent in all of its well-recognized com- 
pounds, a possible hydride has been reported (67) which may have 
the composition ZrH 2 . The existence of a monoxide ZrO, which would 
also be bivalent, has been maintained by some investigators, but the 
evidence for it is not satisfactory. 



Chapter III 

Compounds of Zirconium with the Elements 
Zirconium and Hydrogen 

Zirconium Hydride. The formation of a gaseous zirconium hy- 
dride with a supposed composition corresponding to the formula ZrH 4 
has been reported but on insufficient evidence and without analytical 
data. Later work seems to disprove the existence of such a com- 
pound. 

Winkler (817, 818) prepared a hydride during the reduction of 
zirconia by magnesium in a stream of hydrogen. The product was 
cooled under hydrogen and heated again in an atmosphere of hydro- 
gen. On treating with dilute hydrochloric acid abundant hydrogen 
was obtained by the action of the- acid on unchanged magnesium. A 
peculiar, disagreeable odor was noted. The gas also gave with silver 
nitrate solution a dark precipitate in which no zirconium was de- 
tected. The product left after freeing from magnesium was a black 
powder, unattacked by ordinary reagents, easily filtered, but giving 
a colloidal solution on washing. It was readily oxidized after drying. 
Analyses of several samples showed it to be a mixture of zirconia 
and the metal or hydride with an average of 0.73 p.c. of hydrogen. 
Matignon (469) observed the absorption of hydrogen by zirconium 
when heated and concluded that a hydride had been formed. 

Wedekind (773) noticed that a gas was liberated when the product 
obtained by reducing zirconia with boron was treated with dilute 
hydrochloric acid. It had an unpleasant smell, blackened paper 
moistened with silver nitrite and burned with an almost colorless 
flame. He came to the conclusion that the gas was hydrogen mixed 
with a small amount of boron hydride. 

Wedekind (785) also analyzed a commercial product which was 
claimed to be ZrH 4 . It was a soft, grayish-black powder, burning 
with the formation of water and yielding analytical results which 
agreed with the formula ZrH 2 . He also prepared this hydride by 
heating metallic zirconium in a Heraeus furnace filled with hydrogen 

34 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 35 

under a pressure of one-half atmosphere. The temperature was car- 
ried up to 700 and then slowly lowered. The hydrogen may be en- 
tirely driven off above 800. The dissociation temperature, therefore, 
lies between 700 and 800. The evidence seems to be against this be- 
ing merely absorbed hydrogen and such as to admit of the conclusion 
that zirconium forms a definite hydride in which it is bivalent. This 
would correspond with the known hydrides in the fourth group, TiH 2 , 
LaH 2 , and ThH 2 , though some of these may also require further proof 
of their existence, but the existence of such a compound lacks con- 
firmation. 

Zirconium and Oxygen 

Zirconium Oxide. The only definitely known oxide of zirconium 
is the dioxide or zirconia, Zr0 2 , corresponding to C0 2 , Si0 2 , Ti0 2 , 
and the oxides formed by the other members of the fourth group. 
There is no satisfactory evidence of the existence of a suboxide, ZrO. 
Certainly no such oxide has been prepared or separated, though sev- 
eral investigators have inferred its existence in order to explain ob- 
servations made by them. For instance, the readiness with which 
the metal, as prepared by the magnesium reduction, oxidizes when 
exposed to the air has been assumed as due to the presence of this 
monoxide, but a pyrophoric condition is not unusual with metals in a 
state of fine subdivision. Also the increase in weight when oxidized 
has been taken as a measure of the total oxygen present in combina- 
tion and from this a formula ZrO calculated (767) whereas the origi- 
nal product of the reduction in preparing the metal was most prob- 
ably a mixture in unknown proportions of zirconium, zirconia, and 
zirconium hydroxide, and hence the data were insufficient for calcu- 
lation. Schwarz and Deisler (653) have shown that a monoxide is 
not formed by the reduction of zirconia by magnesium but a mixture 
of zirconia and the metal together with a small amount of magnesium 
zirconide. The migration of the so-called colloidal zirconium, as 
observed by Whitney and Oder (815) in the direction of the negative 
stream has been cited as a further argument for the existence of ZrO, 
but this is at variance with the observations of Wedekind (777). 
Besides, the exact nature of this colloidal zirconium seems to vary 
somewhat according to the method of preparation and there are indi- 
cations that at times zirconia is present, or rather the colloidal hydrox- 
ide. Wedekind (780) seems to have failed to obtain ZrOCl 2 by the 
chlorination of the colloidal solution prepared by the Berzelius 



36 ZIRCONIUM AND ITS COMPOUNDS 

method, which would be expected to form if ZrO were present. The 
oxide, ZrO, therefore, is not known to exist separately but, as will be 
seen later, the radical zirconyl is found in a large number of com- 
pounds. 

Zirconium Dioxide. This oxide, Zr0 2 , known as zirconia, occurs 
uncombined in small amounts in Ceylon and other localities, and in 
commercial quantities in Brazil at Jacupiranga, in the State of Sao 
Paulo, and also in the State of Minas Geraes. It is known miner- 
alogically as baddeleyite, and that which comes from Brazil as brazil- 
ite. The ore is found in alluvial pebbles from one-half to three 
inches in diameter, containing from 90 to 93 p.c. of zirconia. It is 
found also in a form in which there is a larger percentage of zircon 
and another silicate differing from zircon by its solubility in hydro- 
fluoric acid. This ore, a mixture of brazilite, zircon, and zirkelite, 
is known as zirkite and carries from 80 to 85 p.c. of zirconia. This 
native zirconia contains helium and argon besides carbon dioxide, 
nitrogen, oxygen, and hydrogen. The abundance and lesser cost of 
this zirkite make it the chief commercial source of zirconia and the 
other compounds. Apart from this native zirconia the only other 
practical source of zirconia is the zircon, at present mined only in 
the United States in the mountain regions of North Carolina. This 
is found chiefly in Henderson County in a pegmatitic dyke which is 
about 100 feet wide. The upper portions of the dyke are much 
decomposed and kaolinized to a depth of 40 feet or more. The zir- 
cons are well crystallized, easily separated by hand and washed free 
from soil. There is no systematic mining carried on and only a few 
tons have been shipped out. 

Purification of native zirconia. For many purposes native zir- 
conia can be used without further treatment. Such uses, for instance, 
are as a refractory and for furnace linings. However, for the prepa- 
ration of enamels, salts, and for other uses requiring purity of ma- 
terials the impurities must be separated. By fusion with an alkali 
hydrogen sulphate and leaching with water acidulated with sulphuric 
acid a solution of the sulphate is obtained. Much of the iron present 
may be removed by using a small amount of water for the first wash- 
ing and rejecting this. The solution of the sulphate yields the hydrox- 
ide on the addition of ammonia solution. This is dissolved in dilute 
hydrochloric acid and the zirconyl chloride purified by recrystalliza- 
tion from concentrated hydrochloric acid. On ignition of the chloride 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 37 

zirconia is left, but small amounts of chlorine are persistently re- 
tained. 

A more economical method has been patented for large-scale pro- 
duction (330) . The ore is heated with excess of lime and an amount 
of carbon insufficient for the reduction of the lime. Calcium carbide 
may be used in the place of the carbon. The product is treated with 
hydrochloric acid, the silica removed, and the zirconyl chloride then 
purified. Other methods of preparation are referred to under Patents. 
(See 12, 29, 250, 310, 330, 380, 444, 454.) 

Preparation of zirconia from zircons. The most direct method is 
by subjecting powdered zircons to the high temperature of the electric 
furnace. The silica and oxides of iron and certain other metals are 
volatilized and the zirconia is left in quite a pure condition. This 
method was first suggested by Troost (715) . There is loss of zirconia 
by volatilization at a very high temperature. 

Finely powdered zircon can be brought into solution by fusion. 
A number of different fluxes have been utilized. Marignac (468) 
prepared the fluoride by fusing powdered zircon with an excess of 
potassium hydrogen fluoride. The melted mass was allowed to cool, 
powdered, boiled with water to which some hydrofluoric acid had 
been added, and the potassium fluozirconate crystallized out. On the 
addition of sulphuric acid, evaporating to dryness, and igniting 
strongly there was obtained a mixture of zirconia and potassium sul- 
phate from which the latter could be removed by leaching with water. 
Or, as recommended by Hornberger (324), the evaporation can be 
carried to a point at which all of the hydrofluoric acid and most of 
the sulphuric acid have been driven off, then dissolved in water, and 
precipitated by ammonium hydroxide. 

A more satisfactory method (733) is to fuse in a nickel crucible 
400 grams of NaOH, 20 grams of Na 2 F 2 , and 100 grams of powdered 
zircon which will pass through a 100-mesh screen. The heat of an 
ordinary burner is sufficient and the decomposition takes place in 
from ten to fifteen minutes. The sodium fluoride should of course 
be well dried. The sodium hydroxide is first melted and the fluoride 
then added. After bringing the melted mass to a fairly high tem- 
perature the zircon is gradually added. Rapid evolution of gas fol- 
lows the introduction of the powder, the mass being kept well stirred 
by a nickel stirrer. Much seems to depend upon the reaction being 
carried through rapidly at a high temperature. The amount of un- 
attacked zircon should not exceed 0.5 p.c. The melted mass is poured 



38 ZIRCONIUM AND ITS COMPOUNDS 

out upon pieces of sheet nickel. While still hot it is broken off and 
plunged into hot water. The sodium zirconate is left undissolved, 
though a negligible portion will go into solution. This zirconate is 
then dissolved in dilute hydrochloric acid and evaporated to dryness, 
this being repeated to separate any silica and to drive off such hydro- 
fluoric acid as remained. The dried mass is leached with dilute 
hydrochloric acid and zirconium precipitated as hydroxide with am- 
monia. This hydroxide is dissolved in hot concentrated hydrochloric 
acid, the solution evaporated to dryness and the crude zirconyl chlo- 
ride washed with ether, thus removing most of the iron present. The 
iron can be reduced to a trace by the phosgene method (762). The 
zirconyl chloride is then repeatedly crystallized from boiling hydro- 
chloric acid. This chloride still retains some silica which may be 
removed by dissolving in water and filtering. Several crystallizations 
from water give a very pure chloride. For the complete removal of 
all impurities it is necessary to transform this oxychloride into the 
tetrachloride and sublime it repeatedly. On ignition the chloride 
yields the oxide, which retains some, chlorine even after prolonged 
heating at 700-800. For the pure oxide it is necessary to pre- 
cipitate the hydroxide, wash, and ignite. 

Fusions of zircon have been made with the caustic alkalies alone 
(45, 202, 480) ; also alkali carbonates (45, 808) ; also potassium 
hydrogen sulphate. Stolba (683) decomposed zircon by heating with 
a solution of sodium hydroxide under pressure. By heating zircon 
in the electric furnace with carbon, or better, lime and carbon, the 
carbide is formed. This can be dissolved in aqua regia and zirconium 
hydroxide precipitated by means of ammonium hydroxide (585, 792). 
The yield is reported as only fair. 

Crystallized zirconia can be prepared by the action of boric acid 
upon zirconium tetrafluoride heated in a carbon crucible. The reac- 
tion is 3ZrF 4 + 2B 2 3 = 3Zr0 2 + 4BF 3 . The boron fluoride is vola- 
tilized and the zirconia is left in the form of dendritic crystals resem- 
bling those of ammonium chloride (184). It has also been prepared 
quite pure as white tetragonal crystals by dissolving zirconia in melted 
magnesium chloride. The crystals separated out on cooling (346) 
as white tetragonal prisms and had a density of 5.74. Moissan (500) 
obtained a vitreous crystalline mass showing dendritic form on frac- 
ture by bringing zirconia to full boiling in an electric furnace by 
means of a current of 360 amperes and 70 volts. Abundant vapors 
of zirconia also came off. The form of zirconia crystals has also 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 39 

been reported (586) as quadratic and hexagonal. Berzelius reports 
zirconia as dimorphous. It has been reported as isomorphic with 
silica. Native zirconia, baddeleyite, is monoclinic, often twinned, 
and with perfect cleavage. It has a negative double refraction, a 
density of 5.41, and hardness of 6 to 7 (360, 361). 

Properties. The heat of formation of zirconia by direct oxidation 
of the metal is: Zr+0 2 = Zr0 2 + 1958.7 cal. (498). It forms a 
white, impalpable powder which is easily swept away in the process 
of ignition; also a rough, coarse powder which is hard to crush com- 
pletely and scratches glass. If prepared by the gradual dehydration 
of the hydroxide and then raising the temperature to 800-1000 it 
forms a compact, semi-vitrified mass. The density has been vari- 
ously reported as 5.45, Hermann; 5.50, Sjogren; 5.49, Venable and 
Belden; 5.85, Nilson and Petterson; 5.66, Ruer; 5.89, Bradford. The 
melting point has been given as 2563 at 30 mm. pressure (626), 2700 
(762), and 2950 (97), and is next to the highest melting point for 
any metallic oxide. The melting point of MgO is 2800. The specific 
heat is 0.1076 (533) and it is diamagnetic (5). It melts and is volatil- 
ized in an electric furnace, and the melting point and beginning of 
vaporization are said to lie quite close together. The boiling and 
vaporization can be readily observed. This boiling point has been fixed 
by Mott (509) at 4300. The coefficient of expansion is low, namely, 
0.00000084, about the same order as that of silica. The conductivity 
for heat and electricity is also low. The porosity is low (under 1 p.c.) 
and vessels made of it are impervious to most liquids. When heated 
in the oxy-hydrogen flame it gives off a very brilliant light with 
comparatively little heat and yields a continuous spectrum. Cob- 
lentz (1,47) has investigated the diffuse reflecting power of zirconia. 

Chemical Conduct. Early attempts to reduce zirconia failed (170, 
711). It is partially reduced on ignition in a reducing flame (29). 
Dissociation begins at about 2500. Ordinary reducing agents, 
such as hydrogen, do not have any action upon it. Its reduction in 
the electric furnace by means of carbon begins at 1400, a carbide 
being formed (257). Boron and silicon also reduce it, forming 
respectively a boride and silicide (723, 791). Various metals, 
such as aluminium and magnesium, also reduce zirconia, partly 
alloying with the metal. Various agents, such as carbon tetrachloride 
and carbonyl chloride, bring about double decomposition, forming the 
tetrachloride and carbon dioxide. 

When mixed with carbon and heated zirconia is acted upon by 



40 ZIRCONIUM AND ITS COMPOUNDS 

chlorine and bromine with the formation of the tetrachloride and 
tetrabromide. It is also acted upon by phosphorus pentachloride 
when heated in a closed tube. When a mixture of chlorine and carbon 
tetrachloride is passed over zirconia heated to 300-400 zirconium 
tetrachloride is formed. 

When zirconia is ignited it becomes practically insoluble in all 
acids except hydrofluoric. The discrepancies in the statements as to 
its solubility in other acids seem to be due to differences in the degree 
of ignition. 

Zirconia is readily dissolved in melted caustic alkalies with the 
formation of zirconates. When added to melted alkali carbonates 
carbon dioxide is evolved, but the formation of zirconates is more 
difficult and only partial. Melting with certain chlorides also yields 
zirconates. When melted with the bisulphates soluble salts or double 
salts are obtained. Those with potassium are more difficultly soluble. 
It is not dissolved in melted boric acid (747) . 

Zirconium and Hydrogen and Oxygen 

Zirconium Hydroxide. This is usually prepared by precipitation 
from a solution of a zirconyl salt. When an alkali hydroxide is used 
it is almost impossible to wash the precipitate entirely free from the 
alkali. Even when ammonia is used prolonged washing is necessary 
in order to secure the pure hydroxide. The precipitated hydroxide 
is bulky and gelatinous, resembling aluminum hydroxide. On dry- 
ing it forms a semi-opaque, vitreous mass, cracking and breaking up 
on shrinking. After draining on the filter it retains as much as 
95 p.c. of water; air-dried, the water content is 47 p.c. (42) ; dried in 
vacuo, there is still left about 20 p.c. of water (171, 536). After 
several weeks' standing over sulphuric acid the weight becomes nearly 
constant. The water content was found to be 22.89 and 23.01 p.c. 
(326, 466). In these experiments the precipitation and washing took 
place in the cold and evidently normal hydroxide was obtained when 
dried over sulphuric acid. The calculated percentage of water for 
Zr(OH) 4 is 22.69. By washing the fresh precipitate once with alcohol 
and then ether the percentage of water was reduced to 26.50; wash- 
ing with petroleum ether the water was reduced to 26.44, a mean of 
several experiments (743). 

Dried at 100, whether precipitated hot or cold, the compound 
ZrO(OH) ? is left (50, 537, 466). This partial dehydration takes 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 41 

place in the hot precipitation when the solution is heated to 85 or 
over (42), the precipitate being dried at 100 (50) or 140 or higher 
(42), representing then a fairly stable compound. This is the zir- 
conyl hydrate. Van Bemmelen reports that there is no further loss 
of water up to 200. At 300 something over one-half p.c. of water 
is left and the last traces of water can be removed only by heating 
to a much higher temperature. The addition of water does not restore 
water of hydration to the once partially dehydrated hydroxide. 

The earlier observation (171) that after all water had been re- 
moved and the oxide was further heated there was a sudden loss of 
potential energy with emission of light has been partially confirmed 
and the conditions more accurately fixed, it having been reported that 
sometimes the phenomenon failed to appear (42, 600). The light 
appears at about 300, but only when the hydroxide has been par- 
tially dehydrated at a somewhat lower temperature, retaining a small 
fraction of the water (less than 1.9 p.c.). The heat of this change, 
ZrO(OH) 2 = Zr0 2 + H 2 0, is about 9.2 cal. to the gram of zirconia. 
When heated higher there are sudden small explosions with the pro- 
duction of extremely fine powder (619). This doubtless partly ac- 
counts for the loss of zirconia in quantitative determinations even 
under all the usual precautionary conditions. 

The normal Zr(OH) 4 , or cold precipitated hydroxide, is practically 
insoluble in water. It is readily dissolved by concentrated or dilute 
inorganic acids to form salts though only sparingly soluble in hydri- 
odic. Among the organic acids oxalic is the most reactive, dissolving 
it nearly as rapidly as some of the inorganic acids. Saturated solu- 
tions of tartaric and citric acids and glacial acetic acid dissolve very 
little (743). 

Zirconyl hydroxide, ZrO(OH) 2 , which is precipitated from hot 
solutions, is more slowly soluble in dilute inorganic acids, dilute hydro- 
chloric or dilute nitric acid dissolving only about 1:100, and dilute 
oxalic acid about half as much.. If, however, the precipitate stands 
for some days in contact with the acid it is dissolved to about the 
same extent as when precipitated cold (743). The chief difference 
noted in the case of concentrated acids is that some act more slowly. 

Ammonia (Sp. Gr. 0.9) does not seem to dissolve the hydroxide 
appreciably. When diluted it dissolves about 1:10,000. Potassium 
or sodium hydroxide have a decidedly greater solvent action, espe- 
cially the latter. Presumably a compound is first formed which is 
then dissolved. If a concentrated solution of an alkali hydroxide 



42 ZIRCONIUM AND ITS COMPOUNDS 

saturated with zirconium hydroxide is diluted a portion of the hy- 
droxide will be precipitated, probably as zirconate (747). Certain 
salts of ammonia exert a greater solvent action than the hydroxide. 
A saturated solution of the commercial carbonate dissolves about 
1 : 100 and an ammoniacal solution of ammonium tartrate has a some- 
what lesser action. The density of the hydroxide precipitated cold 
and containing 25.97 p.c. of water is 3.25 (743). 

Colloidal Zirconium Hydroxide. This colloid has been prepared 
by the dialysis of a zirconyl nitrate solution. The liquid appears 
clear in transmitted light but cloudy in reflected and contains 1.98 
grams of zirconia to the 100 c.c. It is stable when boiled and fairly 
stable towards electrolytes. The hydrosol is positively charged (67, 
68). Also by the dialysis of a zirconyl chloride solution a colloidal 
hydroxide has been obtained (0.6 gram zirconia in 100 c.c.) which 
was clear in both transmitted and reflected light. The hydrosol re- 
tains some chlorine which is not directly precipitated by silver nitrate 
but is protected by the colloid. On attempting to remove the last 
of the chlorine a hydrogel is formed. The chlorine can be precipitated 
after boiling with nitric acid. A largely hydrolyzed zirconium oxy- 
chloride containing 5.5 p.c. chlorine and 87 p.c. zirconia yields in water 
a milky solution in which acids give a precipitate. A colloid can be 
prepared from this solution nearly free from chlorine. The colloidal 
hydroxide is precipitated by such electrolytes as sodium or ammonium 
chloride (619). 

A colloidal hydroxide has also been prepared by boiling a highly 
basic zirconium nitrate with water and filtering. The hydrosol is 
opalescent and on evaporation yields a gummy residue which swells 
and dissolves in water. Slightly ionizing univalent salts have no 
effect upon this hydrosol, but strongly ionizing salts cause coagula- 
tion. Anions of a higher valence cause precipitation. The valence 
of the cation is a negligible factor (512). The dialysis of a 1.5 p.c. 
solution of zirconium acetate gives a clear colloidal solution containing 
0.45 grams of zirconia to the 100 c.c. and very little acetic acid. To- 
wards electrolytes it behaves in the same manner as the preparation 
just described (611). By peptonizing zirconium hydroxide with 
uranyl nitrate a yellowish, milky, strongly opalescent, very stable 
colloidal solution is obtained (695). 

It would seem that in preparing the colloid from these hydrolyzed 
and highly basic compounds some of the surplus of zirconium hydrox- 
ide is separated from the salt. Lottermoser (445), who apparently 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 43 

used a less hydrolyzed solution, failed to secure a hydrosol. Van 
Bemmelen (42) advanced the theory that the zirconium hydroxide 
forms in these highly basic salts an adsorption compound with the 
zirconyl salt. It will be seen later that the hydrolysis progresses in 
a far-reaching manner, though halting places are observed where 
definite compounds seem to be formed. Mliller (512) has suggested 
that opalescent or non-opalescent dilute solutions of zirconyl hydrox- 
ide in salts of zirconium are to be looked upon not as basic but as 
adsorption compounds of the colloidal hydroxide with the salt. These 
salts then yield colloidal solutions and in all of them a hydrogel is 
present. The adsorptive power of zirconium is very considerable 
and comparable with that of aluminum hydroxide. On this account 
its utilization has been proposed in the purification of water, mor- 
danting of textiles, preparation of lac dyes, and for similar purposes. 
Hydrolysis and formation of zirconyl hydroxide. All salts of 
zirconium hydrolyze very readily when dissolved in water with the 
separation of free acid and zirconyl hydroxide. Salts of quadrivalent 
zirconium do not exist in aqueous solution. In such solutions the 
bivalent zirconyl radical is always present. This forms a weak base 
and is amphoteric. Definite proof as to the formation of this hydrox- 
ide is not always available, but the ease with which the normal 
hydroxide is itself dehydrated, especially in even moderately warm 
water, and other facts render this probable. In some cases the zir- 
conyl hydroxide has been separated by dialysis. When the acid is 
volatile it is easily lost on evaporation or when the solution is set 
aside over a caustic alkali absorbent. The hydrolysis is often pro- 
gressive so that the acid constituent may be largely washed away from 
a precipitated insoluble basic salt. In a number of instances the in- 
soluble basic compound is formed only after prolonged standing of 
the solution. This precipitation may be hastened by boiling the solu- 
tion. This may indicate a progressive hydrolysis, the normal hydrox- 
ide being first formed and then dissociated into zirconyl hydroxide 
and water, the insoluble basic salt being a compound of zirconyl 
hydroxide. This being the most plausible assumption, the basic salts 
to be described later will have formulas ascribed to them as com- 
pounds of zirconyl hydroxide. Many of these basic compounds form 
crystals whose composition can be definitely determined or precipi- 
tates in which the composition is little changed by repeated washings. 
Some form neither crystals nor precipitates but leave a gummy mass 
on evaporation. In such masses indications of crystalline structure 



44 ZIRCONIUM AND ITS COMPOUNDS 

are sometimes to be found. The custom has often been followed of 
reporting the basic compounds with formulas containing Zr0 2 . There 
would seem to be little justification for the use of this or of the easily 
dehydrated Zr(OH) 4 . Some of the salts would seem to be adsorption 
compounds with colloidal ZrO(OH) 2 and lacking in definite composi- 
tion. 

On heating a zirconium salt of a volatile acid, such as hydrochloric 
or sulphuric, to a temperature of 500 to 800 most of the acid is 
eliminated but. traces of these acids are held even after prolonged 
ignition (744) . The amount retained is ordinarily too small to inter- 
fere materially with analytical results. 

Higher Oxides of Zirconium. 1. Zr0 3 was obtained in the hy- 
drated form as a white precipitate by Cleve (146) on adding hydrogen 
peroxide to a solution of zirconium sulphate made alkaline by am- 
monium hydroxide. The precipitate was dried over sulphuric acid 
and potassium hydroxide and gave on analysis 13.12 p.c. of oxygen 
in excess of Zr0 2 , which corresponds closely with the amount calcu- 
lated for Zr0 3 . Bailey (22) on repeating this experiment used an 
acid solution so as to avoid the possible presence of zirconium hydrox- 
ide from the excess of ammonia. He also obtained a bulky, white 
precipitate which, on being heated gently with hydrochloric acid and 
potassium iodide, liberated iodine. This precipitate, after thorough 
washing, was allowed to stand three months. The analysis yielded 
69.46 p.c. of zirconium and 30.54 p.c. of oxygen. A freshly precipi- 
tated preparation gave closely concordant results. These correspond 
with the formula Zr 2 5 . Further determinations of the combined 
water gave the complete formula as Zr 2 5 .4H 2 0. This is partially 
dissociated on boiling and is insoluble in dilute sulphuric and acetic 
acids. From more dilute solutions the precipitate corresponded to 
ZrO 3 .5H 2 0. If this is dried at 100 the analysis corresponds with 
Zr0 3 (22). 

Piccini (549) failed to get such precipitates. It has been sug- 
gested (238) that the solutions used by him were too dilute and that 
the compound Zr 2 5 obtained by Bailey was perhaps a decomposition 
product. Geisow (238) also confirmed the results of Cleve, using a 30 
per cent solution of hydrogen peroxide and precipitating in solution 
made alkaline. Pissarjewski (554) , who prepared Zr0 3 (hydrated) by 
precipitation with H 2 2 in an ammoniacal solution at a temperature 
of to 3, stated that the trioxide loses active oxygen on standing 
and that it is entirely lost at 75. The heat of formation is given as 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 45 

-21.786 cal. The formation of this precipitate with hydrogen per- 
oxide has been recommended as a means of quantitative separation 
of zirconium from iron (238, 775). 

The trioxide has also been prepared by the action of hydrogen 
peroxide on an alkali tartrate solution (775, 293) ; by its action upon 
zirconyl hydroxide or the action of sodium hypochlorite on zirconyl 
nitrate at 8-10; and by the electrolysis of an alkaline solution of 
sodium chloride in which zirconyl chloride is suspended (549). It 
forms a gelatinous precipitate which is decomposed on standing over 
sulphuric acid or soda lime. 

Zirconium and Nitrogen 

Zirconium Nitride. Zirconium shows a strong affinity for nitro- 
gen. The metal readily combines with it when heated in a stream 
of nitrogen or when heated in the air. Thus the earlier attempts at 
preparing zirconium yielded products containing the nitride, as air 
was not rigidly excluded. On exclusion of nitrogen no nitride was 
formed (818). The evidence as to the presence of nitride was the 
formation of ammonia on treatment with a caustic alkali. When the 
carbide is heated in nitrogen the carbon is displaced and a nitride 
formed (779). The nitrides heated in a stream of hydrogen yield 
ammonia and the metal (473). 

The formation of the nitride was observed by Wohler (820) 
in 1839. In 1859 Mallet (463) in attempting to prepare zirco- 
nium by the reduction of the oxide with aluminum in a lime crucible, 
which cracked, obtained a product which on treating with hydrochloric 
acid left undissolved iron-black, lustrous leaflets and a golden-colored 
substance. The latter was in the form of microscopic cubes which 
were slightly attacked by acids and caustic alkalies and showed a 
slight formation of ammonia when left under water. By heating 
amorphous zirconium in a stream of ammonia until the glass tube 
softened he obtained a product which gave off ammonia abundantly 
when fused with caustic alkali. Heated in the air it burned to zir- 
conia. A similar product was prepared by heating zirconium chloride 
in a stream of ammonia. Zirconium heated in a stream of cyanogen 
gave a dark, amorphous powder which gave off ammonia abundantly 
on fusion with caustic alkali and burned to a white powder in air. 
He believed the cyanogen formed a nitride though possibly admixed 
with cyanide. No analyses were reported. 



46 ZIRCONIUM AND ITS COMPOUNDS 

Matthews (473) heated ZrCl 4 .8NH 3 to redness in a stream of 
nitrogen. Abundant fumes of ammonium chloride were given off. 
The residue, a pearl-gray powder, yielded ammonia when heated in a 
stream of hydrogen. The nitrogen present was determined by dis- 
solving this gas in a standard solution of hydrochloric acid. The 
residue was burned to zirconia and weighed. The analysis corresponds 
with the formula Zr 3 N 8 . When ZrCl 4 .4NH 3 was treated in the same 
way the analysis of the product gave Zr 2 N 3 . 

Wedekind (777) found that when magnesium was heated in the 
air with zirconia a greenish-brown crystalline powder was left. This 
glowed on gentle heating and when scattered in a flame burned with 
scintillations. It was notably stable towards acids, excepting hydro- 
fluoric, and did not conduct electricity. On fusing with alkalies am- 
monia was given off. The analysis corresponded with the formula 
Zr 2 N 3 . 

Bruyere and Chauvenet (110) have shown that all ammonia com- 
pounds with zirconium tetrachloride yield Zr(NH 3 ) 4 Cl 4 on heating 
up to 195. This is true also of the iodide. At higher temperatures 
the halogen acid and not ammonia is given off. Thus at 225-250 
the amide Zr(NH 2 ) 4 is formed in an atmosphere of hydrogen or am- 
monia. Above 250 the product seems to be a mixture of an imide 
and a nitride, Zr(NH) 2 + Zr 3 N 4 . At 350 only the Zr 3 N 4 remains. 
This is insoluble and unchanged in water. According to these ob- 
servers the nitride, Zr 3 N 8 , reported by Matthews is to be regarded as 
a mixture of the amide Zr(NH 2 ) 4 and the imide Zr(NH) 2 . 

Wedekind (785), in examining the properties of the purest 
zirconium he could obtain, found that nitrogen shows little action 
upon powdered zirconium under 1000. There is practically no change 
at 500; at 700 1 p.c. is changed; at 800 4 p.c.; at 1050 to 1080 
9 p.c. The product at this temperature is Zr 3 N 2 . The same nitride 
is given by ammonia at 1000. It is a crystalline powder with metal- 
lic lustre, more resistant to oxygen and chlorine than zirconium, with 
about the same resistance to acids. Solutions of alkalies show no 
action, but fusion with caustic alkalies yields ammonia. It is stable 
when heated in a hydrogen stream up to 1000. It conducts elec- 
tricity. 

Curtius (157) has stated that on adding a solution of sodium 
azide (NaN 3 ) to a solution of zirconium sulphate a precipitate of 
zirconium hydroxide is formed and no zirconium is left in the filtrate. 
The azide was not formed by this method. 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 47 

The nitrides reported are Zr 3 N 2 , Zr 2 N 3 , Zr 3 N 4 , and Zr 3 N 8 . In 
addition there are the amide Zr(NH 2 ) 4 and the imide Zr(NH) 2 . 

Zirconium and Carbon 

Zirconium Carbide. The first observation as to the formation of 
zirconium carbide was made by Berzelius, who, in preparing zirconium 
by means of potassium containing carbon, obtained amorphous zir- 
conium which left a residue of carbon on treatment with boiling hy- 
drochloric acid and gave off an unpleasant-smelling gas containing 
hydrogen. 

Troost (714) heated powdered zircon with carbon in an electric 
furnace, using a current of 35 amperes at 70 volts, and obtained 
metallic-like masses of carbide. The analyses indicated the com- 
position ZrC 2 but did not agree closely and no distinction seems to 
have been made between mixed and combined carbon. The product 
did not alter in the air and was not attacked by water or acids except 
hydrofluoric. If little carbon was used the product did not oxidize 
at red heat in the air. If much carbon was used in its preparation it 
burned brilliantly. 

Moissan (500), on fusing powdered zirconia in an electric fur- 
nace with an excess of carbon, prepared a substance containing 4 to 
5 p.c. of carbon. When this was heated with more zirconia the car- 
bon was eliminated. When rich in carbon it was rapidly decomposed 
by air. Later (501) he mixed the powdered zirconia with carbon 
prepared from sugar, using oil and pressing the mass into a cylinder 
which was then calcined. It was afterwards subjected to the action 
of a current of 1000 amperes and 50 volts. Varying amounts of car- 
bon were used, yielding the same results. The product had a metal- 
lic appearance and was unchanged in moist air even when heated to 
100. The analysis yielded 88.6 p.c. of zirconium and 11.4 p.c. of 
carbon, which agrees with the formula ZrC. The fact that this com- 
position was maintained when the amount of carbon used was varied 
brings still more into question the existence of the ZrC 2 reported by 
Troost. Wedekind (785) obtained the same result as Moissan by 
using a current of 600 amperes, voltage not given. 

The carbide has a hardness between 7 and 9, scratching glass and 
quartz, and its use as an abrasive has been suggested. Chlorine acts 
upon it at 250, bromine at 300, and iodine at 400. At a red heat 
it burns in the air. Sulphur yields a small amount of the sulphide 



48 ZIRCONIUM AND ITS COMPOUNDS 

when heated with this carbide to a red heat. If melted with carbon 
in an electric furnace carbon is dissolved, the excess separating as 
graphite on cooling. Ammonia and water are without action at a 
red heat. Hydrofluoric acid acts readily in the cold. Boiling hydro- 
chloric acid has no action. Nitric acid acts slightly when dilute, but 
the concentrated acid acts immediately and violently and so does 
aqua regia. Sulphuric acid readily decomposes it when heated. 
Nitrates and permanganates attack it readily, and chlorates give an 
explosive mixture when heated. Fused caustic potash dissolves it 
readily. There is no action on fusing with potassium cyanide. 

Wedekind (779) prepared a carbide from native zirconia by mixing 
the finely-ground powder with carbon and heating in an electric fur- 
nace. The product sintered into a metallic-like mass which was stable 
in air, water, and hydrochloric acid but was decomposed by chlorine 
at 300. It was found to contain a small percentage of iron oxide, 
silica, and silicates. After deducting this the analysis agreed well 
with the formula ZrC. It is a good conductor of electricity and its 
use for electrodes has been suggested. As anode it would be quickly 
attacked by oxygen. When heated to a red heat in a stream of 
nitrogen a nitride was formed. Mott (509) has given the boiling 
point of the carbide as 5100. 



Zirconium and Sulphur 

Zirconium Sulphide. The sulphide was first prepared by Ber- 
zelius (53) by heating the metal with sulphur in a vessel previously 
evacuated. When the two were heated in hydrogen there was a slight 
appearance of flame. No details are given as to the composition of 
the product but the impurities in the metal used would necessarily 
render it impure. The sulphide is described as a dark cinnamon- 
brown powder which could not be polished to a lustrous appearance. 
As will be seen later, the pure sulphide is crystalline and has a steel- 
gray color. When fused with caustic potash zirconia and potassium 
sulphide were formed. Hydrofluoric acid dissolved it easily with the 
evolution of hydrogen sulphide. Boiling aqua regia dissolved it slowly. 
Hydrochloric, nitric, and sulphuric acids, as well as a solution of 
caustic potash, gave no reaction. 

Paykull (536) prepared an impure sulphide (containing some 
oxygen) by subliming zirconium tetrachloride in a stream of hydrogen 
sulphide, the presence of oxygen not being entirely excluded. The 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 49 

product was stable in the air and water and burned, when heated, 
with the formation of sulphur dioxide. It was oxidized by aqua regia 
and also by nitric acid. Chlorine gave zirconium tetrachloride and 
sulphur dioxide on the application of heat. Moissan and Lengfeld 
(501) obtained a small amount of the sulphide on heating zirconium 
carbide and sulphur to a dark red heat. Fremy (231), by the action 
of carbon bisulphide upon zirconia at a red heat, prepared zirconium 
sulphide in the form of fine, needlelike crystals of a steel-gray color. 
These showed the characteristics of the product obtained by Ber- 
zelius. They were not decomposed by water nor ordinary acids except 
nitric acid, which oxidized the zirconium readily, giving an abundant 
deposit of sulphur. The formula for the sulphide prepared by these 
methods would seem to be ZrS 2 . Hauser (294) repeated the prepara- 
tion by the method of Berzelius by heating the metal in the vapor of 
sulphur, but in this case also the metal was not pure. 

Zirconium Oxysulphide. The oxysulphide, ZrOS, was also pre- 
pared by Hauser (294) by the reduction of the sulphate (dried at 
400) when heated to a strong red heat in a stream of dry hydrogen 
sulphide. It is. a bright yellow powder with a density of 4.87. If re- 
moved from the tube before completely cooling it caught on fire. The 
analysis (Zr, 65.3 p.c. and S, 22.8 p.c.) agrees with the formula ZrOS. 

Zirconium and Boron 

Zirconium Boride. The boride has been prepared by Tucker and 
Moody (723), who used zirconium gotten by the reduction of the 
double fluoride of potassium and zirconium by means of aluminum. 
Hence their results are impaired by the presence of aluminum as an 
impurity. Fifteen grams of this product were heated with 2.2 grams 
of boron in a carbon crucible for five minutes by a current of 200 am- 
peres at 65 volts. The product was brittle, steel-gray in color, and 
under the microscope appeared as an agglomeration of brilliant, trans- 
lucent to transparent, tabular crystals having a density of 3.7 and 
a hardness of 8. They were slowly attacked by hot concentrated acid 
and aqua regia. The analysis gave 86 p.c. of zirconium, which would 
point to the formula Zr 3 B 4 if these two elements alone were present. 

Wedekind (773) tried the reduction of zirconia by means of 
boron, heating 5 grams of zirconia with 1.1 grams of boron in an 
electric furnace. This yielded a mass which was not homogeneous, 
which scratched glass, and which was fairly stable to hot water. 



50 ZIRCONIUM AND ITS COMPOUNDS 

Dilute hydrochloric acid evolved a gas, burning with an almost color- 
less flame and darkening paper soaked in silver nitrate solution. The 
gas was probably hydrogen with some boron hydride. Concentrated 
sulphuric acid was reduced, evolving sulphur dioxide. When the ex- 
periment was repeated at a higher temperature and a more prolonged 
exposure there was formed a gray-black mass which was acted upon 
by hydrochloric acid only on strong boiling. The gas formed burned 
with a green flame. The mass was not acted upon by sulphuric acid 
in the cold but evolved sulphur dioxide on strong heating, which 
would happen if free carbon was present. Dark crystals were formed 
when the mass was dissolved in melted copper and allowed to cool. 
On analyzing the original mass it was found to contain 30.16 p.c. 
of carbon and 57.9 p.c. of zirconium. If the carbon is regarded as 
admixed and the zirconium is calculated carbon-free, the percentage of 
zirconium becomes 82.8 and this approximates the required percentage 
in Zr 3 B 4 . The product may be regarded as a boride mixed with 
carbon or as a borocarbide. The experiments do not afford a satis- 
factory basis for a decision. 

Zirconium and Silicon 

Zirconium Silicide. The preparation of the silicide by the action 
of silicon upon zirconia was tried by Wedekind (773) with only par- 
tial success. When the silicon was added in accordance with the 
equation Zr0 2 + Si = Si0 2 +Zr and heated in an electric furnace a 
dark, compact mass containing undecomposed zirconia was formed. 
With an excess of silicon the regulus had a metallic lustre with crys- 
talline fracture. The broken surface showed silvery crystals. These 
crystals were very resistant to chemical action and recrystallized on 
sublimation. By mixing equivalent weights of zirconium and silicon 
and heating in vacuum to 1000-1200 a homogeneous, gray, slightly- 
sintered powder was obtained (791) . Treating this with warm caustic 
potash excess silicon was removed and the silicide remained. 

Honigschmid (354) has prepared the silicide by heating in a 
Perrot furnace a mixture of potassium fluosilicate (120 grams), the 
double silicate of potassium and zirconium (15 grams), and aluminum 
(50 grams) . The product was in the form of very brilliant metallic 
crystals, which were separated from aluminum and silicon by alternate 
treatment with hydrochloric acid and a solution of potassium hydrox- 
ide. The crystals still retained a small amount of aluminum some 



COMPOUNDS OF ZIRCONIUM WITH THE ELEMENTS 51 

2 or 3 p.c. due doubtless to the formation of a zirconium- aluminum 
alloy. These crystals were small and of a clear iron-gray color. They 
formed rhombic columns with a prism of 58 30' terminated by a 
longitudinal and a transverse dome. The density was 4.88 and the 
hardness approximately that of felspar. They remained unaltered 
in air. When heated on platinum foil they were apparently unchanged 
but burned if previously ground to a fine powder. When the products 
of combustion were treated with hydrofluoric acid a brown residue 
of amorphous silicon was left. Heated in oxygen the crystals burned 
readily, forming silica and zirconia. Fluorine acted upon them at a 
slightly elevated temperature with the appearance of a flame. Chlo- 
rine attacked them at a red heat, and bromine and iodine only at a 
high temperature but without incandescence. Ordinary acids were 
without action, except hydrofluoric acid, which dissolved them with 
the liberation of hydrogen. Solutions of alkaline hydroxide were 
without action, but when fused in alkali hydroxides they were 
readily decomposed. Potassium bisulphate showed no action. 

By using the thermite process Honigschmid (354, 355) obtained 
still better results. Pure, iron-free sand (180 grams) was mixed with 
zirconia (20 grams), sulphur (250 grams), and pure aluminum (200 
grams) in a Hessian crucible, covered with magnesium powder, and 
ignited. It was heated to a white heat. The silicon and silicide 
collected at the bottom of the crucible. After cooling this regulus 
was separated from the aluminum sulphide, broken up and powdered, 
and then treated alternately with hydrochloric acid and 10 p.c. potas- 
sium hydroxide solution in a water bath. The aluminum and silicon 
dissolved and analysis showed much less aluminum retained. The 
zirconium silicide prepared in this way was identical in properties 
and composition with that obtained in the Perrot furnace. The 
analysis gave zirconium 61.8 p.c. and silicon 38.2 p.c. with a trace 
of aluminum. The formula, therefore, is ZrSi 2 . Wedekind and 
Pintsch have patented a process for the commercial preparation of 
the silicide (791). 

Zirconium and Phosphorus 

Zirconium Phosphide. Gewecke (243) has prepared zirconium 
phosphide by subliming zirconium tetrachloride in an atmosphere of 
phosphine. The reaction was carried out in a piece of glass tubing. 
The properties of the phosphide are closely parallel to those of the 
corresponding titanium compound prepared by the same method. 



52 ZIRCONIUM AND ITS COMPOUNDS 

It is a gray, glistening substance somewhat like the hammer scales 
from copper. The density is 4.77 and it is hard and brittle. It is 
stable in air and unaffected by water. The phosphide resists ordi- 
nary chemical reagents and conducts electricity. The analysis showed 
40.18 p.c. of phosphorus and 59.78 p.c. of zirconium, which agrees with 
the percentages calculated for ZrP 2 . 

Attempts at preparing the phosphide by subliming the zirconium 
tetrachloride over potassium phosphide in a stream of hydrogen failed 
to yield a definite compound with constant proportions. An energetic 
reaction took place with appearance of flame, and there was left a 
black mass out of which potassium chloride was leached with water. 
A graphite-like substance was left and this was found to contain some 
oxygen. 



Chapter IV 

Compounds with the Halogens and Their Acids 
Zirconium and Fluorine 

Zirconium Fluoride. Zirconium fluoride, ZrF 4 , was first pre- 
pared by Berzelius (50) by dissolving zirconia in hydrofluoric acid 
until the liquid gave none or only a slightly acid taste. Crystals 
were obtained by evaporating the solution. He stated that the crys- 
talline salt was resolved by water into an acid salt and a basic salt, 
the latter being insoluble. On boiling the solution a partial precipita- 
tion took place and the liquid became more acid. The hydrolysis of 
zirconium salts in aqueous solution was thus distinctly recognized 
and the accompanying phenomena recorded with the accustomed care 
and accuracy of the great master. The crystalline substance reported 
by Berzelius as easily soluble was unquestionably the hydrate 
ZrF^SH^O, as ZrF 4 is only slightly soluble. According to his view 
of the composition of the oxide, namely, Zr 2 3 , his formula for the 
fluoride would be given as Zr 2 F 3 . 

Deville (181) prepared the fluoride by treating with hydrogen 
chloride a mixture of powdered zircon and fluospar placed in a carbon 
boat and enclosed in a carbon tube. He obtained colorless, transpar- 
ent crystals, apparently belonging to the hexagonal system but im- 
perfectly formed. The small crystals were hard to measure. He 
reported them as insoluble in water, not attacked by acids, and vola- 
tile at a white heat. Later, in conjunction with Caron (184) he 
prepared the fluoride by passing hydrogen fluoride over powdered 
zircon heated to a white heat in a carbon crucible. 

Marignac (468) obtained the anhydrous fluoride by heating 
zirconia with ammonium fluoride or ammonium-zirconium fluoride. 
Wolter (824) prepared the fluoride by heating the ammonium-zirco- 
nium fluoride, 2NH 4 F.ZrF 4 , driving off the ammonium fluoride, and 
purifying the zirconium fluoride by sublimation in a stream of hydro- 
gen. A still better method used by him depended upon the double 
decomposition taking place between zirconium tetrachloride and hy- 

53 



54 ZIRCONIUM AND ITS COMPOUNDS 

drogen fluoride, both carefully freed from water and heated in a tube. 
The analysis agreed with the formula ZrF 4 . On subliming small, 
strongly refracting crystals were obtained having a density of 4.43 
at 16. The molecular weight at 1200 was 166.1. It was found that 
1.388 grams dissolved in 100 c.c. of water at ordinary temperature 
without visible change. At 50 hydrolysis took place and a white 
precipitate formed. The only hydrate obtained agreed with the 
formula ZrF 4 .3H 2 0. With liquid ammonia a white pulverulent com- 
pound was formed, having the composition 5ZrF 4 .2NH 3 . Gaseous 
ammonia showed no action, nor does this fluoride combine with pyridin 
and similar organic substances as does the tetrachloride. Further- 
more, it has much less power of uniting with other substances than its 
isomorphs, titanium tetrafluoride and stannic tetrafluoride. This 
Wolter attributed to the small molecular volume, 37.5, as compared 
with 44.3 for TiF 4 and 40.7 for SnF 4 , having the same number of atoms 
condensed in a smaller volume and hence less freedom of motion. 

Zirconium fluoride, if not too strongly ignited, is readily soluble 
in water. Crystals form on gently evaporating this solution acidu- 
lated with hydrofluoric acid. These crystals, which have a com- 
position equivalent to ZrF 4 .3H 2 0, can be redissolved and recrystal- 
lized without change. On account of this fact it has been maintained 
that the fluoride does not undergo hydrolysis, overlooking the early 
experiments of Berzelius which indicate clearly an hydrolysis. 

Chauvenet (127) has made a study of the supposed compound 
ZrF 4 .3H 2 and has come to the conclusion that it is more probably 
a derivative of zirconyl and has the composition ZrOF 2 . H 2 F 2 . 2H 2 0, 
a rearrangement of the same atoms in the molecule. It is stable in 
air and in vacuo but begins to lose water at 100. At 140 it has the 
composition ZrOF 2 .H 2 F 2 but above this temperature it loses hydro- 
fluoric acid and becomes ZrOF 2 . This compound re'combines with 
hydrofluoric acid when placed in the cold acid and regains its former 
composition. In other words, the fluoride behaves in its action to- 
wards water as the salts of the other halogen acids do. The residue 
left on complete drying and calcination of the crystals is zirconia, 
though it probably retains traces of fluorine. 

Wedekind (784) has observed that in igniting zirconia with hy- 
drofluoric acid to remove such silica as may be present there is a loss 
of part of the zirconia. This loss also occurs when a mixture of hydro- 
fluoric acid and dilute sulphuric acid is used but may be prevented by 
using the sulphuric acid in excess. In the latter case all of the 



COMPOUNDS WITH HALOGENS 55 

fluorine is expelled from combination with the zirconium. If no 
excess is present, ZrF 4 , which is volatile at the temperature of igni- 
tion, may be formed. 

Zirconium Double Fluorides or Fluozirconates. Conclusive evi- 
dence is lacking to decide whether the numerous double fluorides 
formed by zirconium are true fluorzirconates or not. On the basis 
of Chauvenet's work already cited some are zirconyl fluorides, and in 
the following description these will be classified as such. The fluorides 
and double fluorides of zirconium are, in general, isomorphous with 
those of the analogous elements, silicon, titanium, and tin (stannic), 
and Gossner (251, 252) has reported certain regularities existing be- 
tween these compounds. For example, the double fluorides formed 
with zinc fluoride show the following gradations in density. 

ZnSiF 6 .6H 2 ZnTiF 6 .6H 2 ZnZrF 6 .6H 2 ZnSnF 6 .6H 2 
Sp. Gr. 2.139 2.106 2.258 2.445 

The independent existence of a fluorzirconic acid, H 2 ZrF 6 , however, 
has not as yet been proved. 

Double Fluorides of Univalent Elements 

Lithium. Two of these double fluorides have been prepared with 
the proportions 2 : 1 and 4:1+2/3 H 2 0. 

2LiF.ZrF 4 or Li 2 ZrF 6 , Wells and Foote (809). When lithium fluo- 
ride (0.7-2.0 grams) is added to zirconium fluoride (20 grams) hex- 
agonal crystals are formed, showing prism and pyramid and rarely 
a basal plane. Separate preparations were analyzed, yielding results 
in accord with the above formula. This is the normal lithium fluo- 
zirconate Li 2 ZrF 6 . 

4LiF.ZrF 4 .2/3H 2 (809). This salt is formed when the above 
salt is recrystallized. It also forms when lithium fluoride (5-7 grams) 
is mixed with zirconium fluoride (20 grams). It forms a crust of 
very small crystals which appear under the microscope to be homo- 
geneous. In one preparation these crystals were mixed with the 
2 : 1 variety. Both hot and cold solutions were used. On recrystal- 
lizing the small crystals were partially dissociated and some lithium 
fluoride crystallized out. As lithium fluoride is very insoluble only 
a comparatively small amount is dissolved in the solution of zirconium 
fluoride. Hence there is a tendency for the lithium fluoride to sepa- 
rate and the 2 : 1 salt to form. Also, the observations reported and 



56 ZIRCONIUM AND ITS COMPOUNDS 

the divergences in the analyses throw doubt upon the homogeneity 
of the substance. Neglecting the water, it may be written 2LiF . ZrF 4 . 
The zirconium fluoride used in the above experiments and in all that 
follows is of course the hydrated one, and it must be borne in mind 
that doubt exists as to its exact nature, especially as to whether or 
not it is a derivative of the zirconyl radical. If Chauvenet is justi- 
fied in looking upon it as a zirconyl derivative, the analysis would 
tend to prove that under the influence of a stable fluoride readjust- 
ment takes place. It must be noted that some of these salts are re- 
ported as giving off hydrofluoric acid after the water had been 
driven off. 

Sodium. Two double fluorides are known, both anhydrous, with 
the proportions 2:1, 5:2. 

2NaF.ZrF 4 (760). When from one to two parts of sodium fluo- 
ride are added to fourteen parts of zirconium fluoride a crust of minute 
crystals of hexagonal outline, which do not recrystallize, is formed. 
From 0.5 to 2 p.c. of water, supposed to be mechanically included, was 
found in the analysis. The fluorine was estimated by difference. 
This would correspond to the normal fluorzirconate, Na 2 ZrF . 

5NaF.2ZrF 4 (468, 809). This salt was formed under widely vary- 
ing conditions on dissolving together the two fluorides, also (468) 
by double decomposition between sodium chloride and ammonium- 
zirconium fluoride. The crystals are described as showing good, 
sharp forms but very small. They appear distinctly orthorhombic in 
habit, consisting in the main of rather stout prisms made up of two 
prismatic planes and terminated by a rather steep brachydome. In 
another habit, which is rarer, the front pinacoid is broadly developed, 
while the prisms are very small. This type also shows at times a 
pyramid. The plane of the optic axes lies in the base. The optic 
angle is large. The double refraction is very low. In their form the 
crystals strongly recall the figures of chrysolite (olivine) . No loss of 
weight was detected on heating, hence no water was present. There 
was also no loss of weight at red heat. The fluorine was estimated by 
difference. This salt may be written NaF . 2Na 2 ZrF 6 . 

Ammonium. Two double fluorides have been reported 2 : 1 and 
3:1, both anhydrous. 

2NH 4 F.ZrF 4 , Marignac (468). This salt was formed from the 
solution of the -two fluorides. It exists in two modifications, Gossner 
(251). First, hexagonal crystals which are formed on the complete 
evaporation of the solution. These are thin, tabular, with very per- 



COMPOUNDS WITH HALOGENS 57 

feet cleavage, and optically are weakly negative. Second, rhombic 
bi-pyramidal crystals, separate before the hexagonal in the earlier 
stage of the evaporation. These are isomorphous with the correspond- 
ing potassium salt. This compound is unchanged on heating to 100. 
On stronger heating ammonium fluoride_is lost and ZrF 4 is left which 
forms ZrF 4 .3H 2 O on dissolving in water. This is the normal fluo- 
zirconate, (NH 4 ).,ZrF 6 . 

3NH 4 F.ZrF 4 , Marignac (468). This salt is formed when a large 
excess of ammonium fluoride is used. It forms regular octahedra 
and cubic octahedra with simple refraction. When heated to 100 
it is unchanged. The last two ammonium double fluorides, as well 
as the analogous potassium salts, have the same composition as those 
of titanium but are not isomorphous. This salt may be written 
NH 4 F.(NH 4 ) 2 ZrF 6 . 

Potassium. Three double fluorides are known 1 : 1 : H 2 0, 2:1, 
3 : 1. 

KF.ZrF 4 .H 2 0, Marignac (468). This salt is formed only in the 
presence of a large excess of zirconium fluoride. It is decomposed on 
re-solution in water. This solution causes no effervescence on the 
addition of ammonium carbonate. The water of crystallization is lost 
at 100. Heated beyond this temperature hydrofluoric acid escapes. 
The crystals are monoclinic prisms or imperfectly formed, short 
prisms, the angle values showing a wide range. This appears to be a 
zirconyl salt and may be written KF.ZROF 2 .H 2 F 2 . 

2KF.ZrF 4 (53, 468). This is formed when equivalent parts of 
potassium fluoride and zirconium fluoride are mixed. The crystals 
are rhombic pyramidal, generally acicular but showing variations. 
This salt can be heated up to a red heat without loss of weight. At a 
red heat it melts to a paste, giving off hydrofluoric acid, which Marig- 
nac attributed to the moisture in the air. An instructive fact lies in 
the rapidly increasing solubility in water with rise of temperature. 
One hundred c.c. of water at dissolves 0.781 grams; at 15, 1.41 
grams; at 19, 1.69 grams; at 100, 25.00 grams. On cooling a boil- 
ing solution a mass of fine needlelike crystals is formed. If a less 
concentrated solution is cooled slowly the crystals obtained are not 
in a determinable form. 

The salt w r as purified by numerous recrystallizations and several 
analyses made by the usual method adopted by Marignac of adding 
sulphuric acid, igniting, and weighing the zirconia from which the 
potassium sulphate had been leached. In the filtrate the potassium 



58 ZIRCONIUM AND ITS COMPOUNDS 

sulphate was determined but the fluorine was calculated from the 
amount necessary to combine with the potassium and zirconium. The 
formula may be written K 2 ZrF 6 , the normal fluozirconate. 

3KF.ZrF 4 . This salt is formed when an excess of potassium fluo- 
ride is used. The crystals are in the form of small, regular octahedra 
and cubic octahedra, usually the first. Not only do the crystal angles 
agree with those of the regular system but they show no double 
refraction. They decrepitate on heating to a red heat, but if previ- 
ously pulverized and dried they suffer no loss of weight. The anal- 
yses of Marignac (468) and Berzelius (53) agree as to their com- 
position. The formula may be written KF.K 2 ZrF 6 . 

In preparing these three compounds then the first is formed in 
the presence of an excess of zirconium fluoride, the last when the 
potassium fluoride is in excess, and the second when the proportions 
lie between these two extremes. 

Rubidium. Two double fluorides are known in the proportions 
2 : 1 and 3 : 1. 

2RbF.ZrF 4 . Behrens (37) prepared this salt by adding rubidium 
chloride to a solution of zirconium sulphate to which ammonium fluo- 
ride and free hydrofluoric acid had been added. The salt crystallizes 
in right-angle prisms. This is the normal fluozirconate Rb 2 ZrF 6 . 

3RbF.ZrF 4 . This compound is formed when the proportions in 
the mixture are changed and crystallizes in strongly refracting octa- 
hedra. The formation of these salts was used by Behrens in his 
microchemical reactions for detecting rubidium. The formula may 
be written RbF.Rb 2 ZrF 6 . 

Ccesium. Three double fluorides are known, with the proportions 
2:1, 1:1: H 2 0, and 2:3: 2H 2 0. Wells and Foote (808) have 
prepared these salts by mixing the solutions of the respective fluorides 
in varying proportions and adding more or less of hydrofluoric acid 
to the sufficiently concentrated solution. 

2CsF.ZrF 4 . By the use of an excess of cesium fluoride this salt 
was formed even when small amounts of zirconium fluoride were 
present. It crystallizes in large plane hexagonal tables, exhibits nega- 
tive double refraction, and can be recrystallized without change. This 
is the normal fluozirconate Cs 2 ZrF 6 . 

CsF . ZrF 4 . H 2 O. This salt is obtained by using larger proportions 
of zirconium fluoride than in the preparation of the foregoing com- 
pound. Monoclinic crystals are formed which also recrystallize with- 
out change. 



COMPOUNDS WITH HALOGENS 59 

2CsF.3ZrF 4 .2H 2 0. When a large excess of zirconium fluoride was 
used very small, difficultly-soluble crystals separated out. These 
were too small to determine crystallographically but showed some 
action upon polarized light. On recrystallization they were partially 
changed into the 1 : 1 compound. In analyzing these salts all 
of the constituents were determined. This salt may be written 
Cs 2 ZrF 6 .2(ZrOF 2 .H 2 F 2 ). 

Thallium. Thallium (809) forms four double fluorides or fluo- 
zirconates having the proportions 1:1, 1:1: H 2 0, 5:3: H 2 0, and 
3: 1. 

T1F . ZrF 4 and T1F . ZrF 4 . H 2 0. When one part of thallium fluoride 
is added to a concentrated solution of three or four parts of zirconium 
fluoride needlelike crystals are formed containing one molecule of 
water if the solution is cooled before crystallization. When the solu- 
tion is evaporated until crystallization begins and then cooled the 
anhydrous salt is deposited in minute square plates. On recrystalliz- 
ing the salt of the 5 : 3 types, having the composition 5TlF.3ZrF 4 .H 2 0, 
is deposited. This salt crystallizes in needles when one to three and 
a half parts of thallium fluoride are added to a solution of one part 
of zirconium fluoride. If as much as four parts of thallium fluoride 
are used the same salt crystallizes in prisms of hexagonal outline, 
which under the microscope are seen to be twinned, and in this respect 
resemble the hexagonal-shaped crystals of aragonite. On recrystal- 
lization both give the needle-shaped crystals. Analyses of the dif- 
ferent forms show that they have the same composition. 

3TlF.ZrF 4 . This compound crystallizes in brilliant octahedra 
when the solution of four to twenty parts of thallium fluoride are 
added to a solution of one part of zirconium fluoride. It recrystallizes 
without change. The following formulas may be ascribed to these 
various compounds: (1) TlF.ZrF 4 ; (2) T1F . ZrOF 2 . H 2 F 2 ; (3) 
TlF.2Tl 2 ZrF 6 .ZrOF 2 .H 2 F 2 ; (4) TlF.Tl 2 ZrF 6 . 

The compounds formed with the univalent metals fall into several 
types. First, there is the normal fluozirconate, M 2 ZrF 6 . This may 
crystallize with a molecule of the alkali fluoride, MF.M 2 ZrF 6 . 
With potassium, cesium, and thallium zirconyl fluoride may 
enter into the composition. Thus we have KF.ZrOF 2 .H 2 F 2 , 
Cs 2 ZrF 6 .2(ZrOF 2 .H 2 F 2 ), and T1F . ZrOF 2 . H 2 F 2 , and lastly T1F. 
2Tl 2 ZrF 6 .ZrOF 2 .H 2 F 2 . 

Double Fluorides with the Bivalent Elements. All of these com- 
pounds crystallize with water of crystallization. 



60 ZIRCONIUM AND ITS COMPOUNDS 

Copper. Two double fluorides have been prepared having the 
proportions 3:2: 16H 2 0, and 2 : 1 : 12H 2 0. 

3CuF 2 .2ZrF 4 .16H 2 O. This salt was obtained by Marignac (468) 
on adding an excess of zirconium fluoride to a solution of copper 
fluoride prepared by dissolving copper carbonate in hydrofluoric acid. 
On evaporation there were formed large crystals of the double fluo- 
ride accompanied by a pale blue crust, which was almost insoluble 
in water and which seemed to be zirconium fluoride impregnated with 
the copper salt. The water of crystallization in the large crystals is 
lost on heating. These crystals form oblique, rhombic prisms of a 
beautiful blue color. 

2CuF 2 .ZrF 4 .12H 2 0. This salt formed on adding copper fluoride 
to the preceding compound (468). It dissolved easily in cold water 
without .change but was dissociated on boiling the solution, depositing 
crystals of copper fluoride and afterwards those of the 3 : 2 : 16H 2 
compound. The original crystals, of a beautiful blue color, are in 
the form of oblique, rhombic prisms and are isomorphous with the 
analogous double fluorides of zinc and nickel, though the angles differ 
slightly. 

Magnesium. One double fluoride is known, with the proportion 
1:1: 5H 2 0. 

MgF 2 .ZrF 4 .5H 2 0. This salt was prepared by Marignac (468) 
by the action of magnesia upon an acid solution of zirconium fluoride. 
There is an abundant deposit of the double fluoride mixed with much 
magnesium fluoride. The double fluoride is not very soluble in water, 
as the two salts may be separated by their relative solubilities. 
Crystals of the double fluoride can be gotten by the gentle evaporation 
of their solution. These crystals are small and generally form in 
oblique rhombohedral prisms. Often crystals are found which recall 
the transposed octahedra of the regular system as seen in spinelle. 
The crystals are isomorphous with the corresponding double fluoride 
of manganese. They have also been described by Groth (265) as 
small, brilliant, six-sided monoclinic tables with bent faces. The 
salt is completely decomposed by prolonged heating, leaving a residue 
of zirconia and magnesia. 

Calcium, Strontium, and Barium. These failed to give well-de- 
fined compounds (468), which may be attributed to their insolubility, 
so that they could not be purified by crystallization. When the car- 
bonate of one of the above elements was added to an acid solution of 
zirconium fluoride the carbonate was decomposed and an insoluble 



COMPOUNDS WITH HALOGENS 61 

precipitate, which was a mixture of the double fluorides and the zir- 
conium fluoride, was formed. When barium chloride was added to a 
solution of potassium-zirconium fluoride a precipitate formed imme- 
diately. The analysis of the precipitate pointed to the formula 
3BaF 2 .2ZrF 4 .2H 2 0, but no decision could be reached as to whether 
it was a compound or a mixture. Similar insoluble precipitates were 
obtained in the case of calcium and strontium. 

. A similar insoluble precipitate was obtained (468) in the case 
of lead. Some of the salt, however, went into solution and a granular, 
somewhat crystalline deposit was obtained on evaporation. This was 
decomposed by water and more rapidly by hydrofluoric acid, which 
precipitated lead fluoride. Other than this no distinct crystallization 
was observed. The method of preparation used was to add lead car- 
bonate to an acid solution of zirconium fluoride and evaporate the 
liquid. 

Zinc. Two double fluorides have been prepared with the propor- 
tions 1:1:6 H 2 and 2 : 1 : 12 H 2 0. 

ZnF 2 .ZrF 4 .6H 2 0. Details are lacking as to the formation of this 
salt (468, 265, 252). Apparently solutions containing equivalent 
parts of the two fluorides were used in its preparation. It recrystallizes 
in long, hexagonal prisms terminating in rhombohedra. It is isomor- 
phous with the corresponding compounds of silicon and tin (stannic) 
and the analogous chlorides of tin and platinum. It presents an easy 
cleavage along the hexagonal faces and is very soluble in water. On 
heating it is decomposed into the oxides of zinc and zirconium. The 
zinc oxide is removed with difficulty and only imperfectly by treat- 
ment with concentrated hydrochloric acid. 

2ZnF 2 .ZrF 4 .12H 2 0. When an excess of zinc fluoride is used 
this salt crystallizes out. It dissolves easily -in cold water but is 
partially decomposed by boiling, depositing zinc fluoride. The crys-. 
tals are monoclinic prisms and are isomorphous with the correspond- 
ing compound of nickel. The crystals are usually twinned. 

Cadmium. Two double fluorides have been prepared with the 
proportions 1:2: 6H 2 and 2:1: 6H 2 (468) . 

CdF 2 .2ZrF 4 .6H 2 0. This salt crystallizes from a solution of the 
two fluorides where the zirconium fluoride is in excess. On evapora- 
tion there were formed lamellated crystals whose exact habit was not 
determined. Efforts at forming the salt CdF 2 . ZrF 4 . 6H 2 failed. 

2CdF 2 .ZrF 4 .6H 2 0. Crystals of this salt are monoclinic prisms, 



62 ZIRCONIUM AND ITS COMPOUNDS 

isomorphous with the preceding salt and with the corresponding salt 
of manganese. It can be recrystallized without change. 

Manganese. Two double fluorides are known with the propor- 
tions 1:1: 5H 2 and 2 : 1 : 6H 2 (468). 

MnF 2 .ZrF 4 .5H 2 O. This salt is formed when manganese car- 
bonate is added to an acid solution of zirconium fluoride. The crys- 
tals are monoclinic prisms and isomorphous with the magnesium com- 
pound. The cleavage is imperfect and the crystals are sometimes 
tabular and sometimes twinned. 

2MnF 2 . ZrF 4 . 6H 2 (468) . When an excess of manganese carbonate 
and hydrofluoric acid are added to a solution of the preceding salt 
short, thick prisms (monoclinic) of this compound are formed. The 
cleavage is easy. These crystals dissolve in cold water without decom- 
position and do not decompose on boiling the solution. If, however, 
they are treated immediately with hot water they decompose and 
form an abundant deposit of manganese fluoride. 

Nickel. Two double fluorides are formed with the proportions 
1:1: 6H 2 and 2 : 1 : 12H 2 (468). 

NiF 2 .ZrF 4 .6H 2 0. This salt is identical with the fluorsilicate and 
fluostannate of nickel and completely resembles also the correspond- 
ing double fluoride of zinc except as to color, which is green. It 
crystallizes in regular, hexagonal prisms terminated by rhombohedra. 
Cleavage is easy along the faces of the prism. On calcination a mix- 
ture of the oxides of zirconium and nickel is left. The percentage of 
fluorine present was not determined. 

2NiF 2 . ZrF 4 . 12H 2 0. This salt is easily formed in the presence of 
an excess of hydrofluoric acid and nickel fluoride. It redissolves in 
water without change and is not affected by boiling, but on standing 
flocculent nickel fluoride is deposited. It crystallizes with a deep 
emerald green color in oblique, rhombic prisms. 

KF.NiF 2 .2ZrF 4 .8H 2 0. This is the only triple fluoride reported 
(468). These crystals are pale green and in the form of oblique, 
rhombic prisms but with a great many modifications. They are 
deposited, practically quantitatively, on mixing in equivalent propor- 
tions solutions of the double fluorides of potassium-zirconium fluoride 
and nickel-zirconium fluoride, and are very slightly soluble in water. 
If the two solutions are in exactly equivalent proportions the mother 
liquor is entirely decolorized and none of the salts is retained in solu- 
tion. If the solutions are hot and concentrated a mass of the acicular 
crystals of the potassium compound is ordinarily deposited and the 



COMPOUNDS WITH HALOGENS 63 

mother liquor remains green, but gradually the first crystals are redis- 
solved and the triple compound is formed. The analysis is incom- 
plete as to the fluorine. 

There seem to be three types of the double fluorides with the bival- 
ent elements. (1) 2MF 2 .ZrF 4 . 6 or 12 H 2 0; (2) MF 2 . ZrF 4 . 6H 2 ; 
(3) 3MF 2 .2ZrF 4 .(H 2 0) n . 

In view of the presence of water it is reasonable to assume that 
all of these are really combinations with zirconyl fluoride and 
should be written as follows: (1) 2MF 2 . ZrOF 2 . H 2 F 2 . (H 2 0) n ; 
(2) MF 2 .ZrOF 2 .H 2 F 2 .(H 2 0) n ; (3) 3MF 2 . (ZrOF 2 ) 2 .H 2 F 2 . (H 2 0) n . 
These compounds have not been sufficiently investigated to clear up 
this question. 

The experiments of Piccini (550) with hydrogen peroxide may 
properly be given here. When titanium fluoride is treated with this re- 
agent the reaction is a reversible one: TiF 4 + H 2 2 + Ti0 2 F 2 + H 2 F 2 . 
A solution of potassium fluotitanate (2KF.TiF 4 .H 2 0) gives with the 
peroxide on heating 2KF.Ti0 2 F 2 ; also ammonium fluotitanate gives 
3NH 4 F.2Ti0 2 F 2 . Neither zirconium fluoride nor its double fluorides 
give this reaction. 

Zirconium-Silicon-Fluoride. Zirconium hydroxide dissolves slight- 
ly in fluosilicic acid. The filtrate becomes cloudy on standing and 
most of the mass settles out as a jelly. After nearly-completed 
evaporation of the solution pearly-white crystals, which are 'easily 
soluble in water, are formed. The solution clouds on heating (49, 
794, 212). 

Zirconium and Chlorine 

Zirconium Tetrachloride (ZrClJ. Preparation. Zirconium tetra- 
chloride was first prepared by Berzelius (52) by the action of chlorine 
upon metallic zirconium. The reaction begins on gentle heating and 
proceeds with incandescence. The presence of water must be care- 
fully guarded against in this as in any method for preparing this 
salt. It was doubtless due to a failure in this respect that the product 
obtained by him was a white, non-volatile mass only partially soluble 
in water. The method is in general unsatisfactory because of the 
difficulty of procuring pure zirconium. For instance, the metal used 
by Troost (714) undoubtedly carried some aluminum as well as iron. 
The tetrachloride was prepared by Wohler (820), Hermann (319), 
and Hinzberg (337) by heating a mixture of zirconia and carbon in a 



64 ZIRCONIUM AND ITS COMPOUNDS 

stream of chlorine. Instead of using zirconia Wb'hler also used pow- 
dered zircon. In trying this method Melliss (480) reported it difficult 
to separate the silicon tetrachloride an observation confirmed by 
Hornberger (356). This difficulty might have been overcome, as 
Troost and Hautefeuille (718) have shown that silicon tetrachloride 
undergoes double decomposition when heated with zirconia, yielding 
silica and zirconium tetrachloride. Troost has also prepared this salt 
by the action of boron trichloride on zirconia. Smith and Harris 
(663) found that zirconia reacted with phosphorus pentachloride when 
heated in a sealed glass tube exhausted of air. The reaction did not 
begin until the temperature was raised above 150 and was complete 
only after some hours of heating at 190. There was obtained a 
crystalline mass which was a mixture of the tetrachloride and phos- 
phorus oxychloride. Distilled in a stream of chlorine this gave the 
nearly-pure tetrachloride in large crystals one-half inch long. Wede- 
kind (785) obtained the chloride when the nitride was heated in a 
stream of chlorine to a dark red heat, and also (775) by heating zir- 
conium carbide in chlorine. The latter reaction was also noted by 
Moissan and Lengfeld (501). Chauvenet (120) found that carbonyl 
chloride at 400 reduced zirconia, forming the tetrachloride. When a 
mixture of carbon monoxide with excess of chlorine is used (749) the 
reaction is hastened and the initial temperature reduced. Powdered 
zircon* (25) is attacked by carbonyl chloride at 1250-1300. The 
action of a mixture of chlorine and sulphur chloride was applied by 
Bourion (95) to zirconia. The reaction was stated to have taken 
place a little under red heat. The product retains sulphur chloride, 
which produces a red color that can be removed by reheating in a 
stream of chlorine. The action of carbon tetrachloride on metallic 
oxides was noted by Demarcay (174) and, using zirconia, he obtained 
the tetrachloride at the temperature of boiling sulphur. Camboulives 
(115) repeated the experiment, noting 400 as the temperature at 
which the zirconia was attacked. Meyer and Wilkens (491) failed to 
observe -any reaction with zirconia at the temperature of the Glaser 
furnace. The gases formed in the reaction were examined and found 
to be carbon monoxide, carbon dioxide, carbonyl chloride, and chlorine 
when using alumina as the metallic oxide. The carbon tetrachloride 
was introduced by bubbling an inert gas through it. This probably 
accounts for the failure to get a reaction with zirconia, which is more 
difficultly attacked. Lely and Hamburger (440) used carbon tetra- 
chloride and chlorine and reported the reaction as taking place at 800. 



COMPOUNDS WITH HALOGENS 65 

Venable and Bell (744) found this method the most convenient one 
for the preparation of the tetrachloride, passing the stream of chlorine 
through a vessel containing carbon tetrachloride and, thus saturated 
with its vapor, over the zirconia in a glass tube heated by an electric 
sleeve. The reaction began at about 300 and was abundant at 
550-600. The yield is quantitative. They also tried the method, 
which had been used by Chauvenet and others, dependent upon the 
dissociation of dried zirconyl chloride. This drying is best done 
under a stream of hydrochloric acid. The dissociation, 2ZrOCl 2 = 
Zr0 2 + ZrCl 4 , begins at about 300 (according to Lely and Ham- 
burger, 600). The yield in several experiments was less than 10 p.c. 
of the theoretical, due doubtless to failure in meeting the exact con- 
ditions of previous dehydration and subsequent dissociation. 

Properties. Zirconium tetrachloride is a white, crystalline sub- 
stance, easily volatilized at about 300, subliming in clear, bright 
crystals of fair size if care is observed in volatilizing and cooling. The 
vapor density has been determined at 440-450 by Hermann (319). 
and Deville and Troost (185) with only partially satisfactory results. 
No modern determinations seem to have been recorded. On exposure 
to air abundant fumes of hydrochloric acid are given off. The reac- 
tion with water is most energetic, evolving much heat and forming 
zirconyl chloride. Covered with anhydrous hydrofluoric acid and 
heated zirconium tetrafluoride is formed, Wolter (824). The density 
of the solid as determined with carbon tetrachloride at room tem- 
perature (744) is 2.8. It is reported as dissolving in absolute alcohol 
with hissing (356, 337), but neither an alcoholate nor hydrate could 
be obtained from the solution (609). On boiling this solution ethyl 
chloride was liberated (356). If the alcoholic solution is saturated 
with hydrogen chloride organic salts of a zirconium tetrachloride- 
hydrogen chloride of the type M 2 H 2 ZrCl 6 can be formed where M 
is pyridin, chinolin, etc. The tetrachloride is also soluble in ether. 
According to Rosenheim and Hertzmann (611), a molecular com- 
pound was formed with the ether but this was not obtained pure. In 
ethereal solution it can form addition compounds with ammonia and 
various organic bases. Many compounds are also formed with other 
organic substances. 

Addition compounds. With sodium chloride 2NaCl.ZrCl 4 . 

Paykull (536) prepared this compound by heating sodium chloride 
to fusion in contact with volatilized zirconium tetrachloride. 



66 ZIRCONIUM AND ITS COMPOUNDS 

With potassium chloride. By the same method Weibull (794) 
prepared a similar compound with potassium chloride. 

With ammonia ZFCl 4 .8NH 3 .Stahler and Denk (674) found 
that this compound was formed when ammonia was passed for about 
twelve hours over zirconium tetrachloride at 16 until the weight was 
constant. Heat is evolved in the reaction and a white powder is left. 
On heating this ammonia was first lost and then ammonium chloride 
driven off. The powder is very hygroscopic when exposed to air and 
loses ammonia. With water it reacts strongly, ammonium chloride 
being formed and zirconium hydroxide precipitated. Matthews (471) 
obtained ZrCl 4 .2NH 3 by the same method, passing the stream of 
ammonia only two hours. When ammonia is passed over the heated 
tetrachloride (673) a white, unstable compound, ZrCl 4 .3NH 3 , is 
formed below 232. Matthews (471) has reported this method as 
giving ZrCl 4 .NH 3 and, on further heating, as losing ammonium chlo- 
ride and leaving the nitride as final product. He also prepared the 
compound ZrCl 4 .8NH 3 by passing dry ammonia into a solution of 
the tetrachloride in absolute ether. Heat was liberated as a white, 
flocculent precipitate was formed. On drying this salt was found 
stable in the air. Paykull (536) also prepared ZrCl 4 .4NH 3 . 

NOC1, N0 2 , S 2 C1 2 , PC1 3 , PC1 5 , C 2 N 2 , and the nitriles give no 
reaction with zirconium tetrachloride (471, 663). Compounds have 
been formed (471) by passing vapors of organic amines into an ethe- 
real solution of the tetrachloride. 

By saturating absolute alcohol with hydrogen chloride, adding an 
excess of zirconium hydroxide, and heating with a reflux condenser 
a solution was obtained by Rosenheim and Frank (609) which was 
filtered cold and again saturated with hydrogen chloride. This 
formed well-crystallized salts on the addition of concentrated solu- 
tions of pyridin chlorhydrate and quinolinchlorhydrate, with the com- 
position (C 5 H 5 N) 2 H 2 ZrCl 6 and (C 9 H 7 N) 2 H 2 ZrCl 6 , respectively. This 
solution in absolute alcohol, saturated with hydrogen chloride, there- 
fore contains zirconium tetrachloride, but no hydrate of this was 
formed (such as had been reported by earlier investigators working 
under different conditions) nor could any alcoholates be detected. 

Organic amines added to aqueous solutions give the same pre- 
cipitate as ammonia (752, 753). 

Zirconyl Chloride (ZrOCl 2 ). This compound is formed by hydrol- 
ysis when the tetrachloride is exposed to moist air or dissolved in 
water. On crystallizing it combines with water of crystallization. 



COMPOUNDS WITH HALOGENS 67 

It is also formed by dissolving the hydroxide in hydrochloric acid. 
From such a solution colorless, needlelike crystals having a somewhat 
bitter, astringent taste are obtained. If the solution is made strongly 
acid the crystallization is nearly quantitative, the hydrated zirconyl 
chloride being only slightly soluble in concentrated hydrochloric acid. 
The addition of water precipitates this chloride from an acid solution 
and concentrated hydrochloric acid precipitates it from an aqueous 
solution. These precipitates are gradually redissolved on standing, 
this re-solution depending upon the relative proportions of the pre- 
cipitant. 

These crystals have the composition ZrOCl 2 . 8H 2 and form tetrag- 
onal prisms with distinct cleavage (265, 304). They are stable in 
air and effloresce over a dehydrating agent, losing hydrochloric acid 
at the same time. They are easily soluble in water and no precipi- 
tate is formed on heating the solution but hydrochloric acid is liber- 
ated. They are also soluble in ether and alcohol. Dilute hydro- 
chloric acid dissolves them but the concentrated acid has little solvent 
action. 

The existence of several hydrates of zirconyl chloride has been 
reported by different investigators. Some of these are manifestly 
erroneous. The following appear in the literature. ZrOCl 2 .9H 2 
(319); ZrOCl 2 .8H 2 (536); ZrOCl 2 . 6 . 5H 2 (537); ZrOCl 2 .6H 2 
(742); ZrOCl 2 .5.5H 2 (434); ZrOCl 2 .4.5H 2 (479); ZrOCl 2 .4H 2 
(434); ZrOCl 2 .3.5H 2 (122); ZrOCl 2 .3H 2 O (736); ZrOCl 2 .2H 2 
(434, 122). Some of these variations may be accounted for by the 
conditions under which the investigations were carried out, such as 
imperfect drying, range of temperature with possible partial hydrol- 
ysis, loss of hydrochloric acid, and whether dried in air or in a stream 
of hydrogen chloride. The hydrates with 9 and with 6.5 molecules 
of water may be definitely excluded, and quite probably those with 
5.5 and 4.5 molecules. Chauvenet (122) from thermochemical data 
has limited the number to those with 8, 6, 3.5, and 2 molecules of 
water. 

These hydrates have been obtained as follows: 

Normally, the zirconyl chloride crystallizes with 8 molecules of 
water and has the composition ZrOCl 2 .8H 2 0. Such crystals are 
formed whenever the solution is evaporated at ordinary temperature. 
They are also formed on the addition of concentrated hydrochloric 
acid to the aqueous solution. If the solution is concentrated a curdy 
precipitate is formed. The crystals are soluble in boiling hydro- 



68 



ZIRCONIUM AND ITS COMPOUNDS 



chloric acid but are deposited again on cooling, and this recrystalliza- 
tion from boiling hydrochloric acid furnishes a method for the puri- 
fication of the chloride. The crystals of this hydrate may be dried 
in air without loss of hydrochloric acid. In dry air they effloresce 
and the loss of water ceases when, they reach a weight corresponding 
to ZrOCl 2 .6H 2 0. If the dehydration is carried further in a stream 
of dry air at 50 the limit ZrOCl 2 .3.5H 2 is reached (122). If 
heated in a stream of hydrogen chloride at a temperature not exceed- 
ing 125 the composition is ZrOCl 2 .3H 2 (736). If the temperature 
is raised to 150 ZrOCl 2 .2H 2 is left (122). The last of the water 
of hydration is lost at 180-210 (736). 

Hydrolysis of the Chlorides. As has been stated, zirconium tetra- 
chloride when brought in contact with water is quickly hydrolyzed 
to zirconyl chloride. This hydrolysis progresses further. Aqueous 
solutions of zirconyl chloride always have an acid reaction and on 
standing the salt present undergoes progressive hydrolysis even at 
ordinary temperature. This hydrolysis is, of course, affected by such 
conditions as temperature and concentration. Ruer (619) has meas- 
ured this hydrolysis in a one-fourth normal solution of ZrOCl 2 .8H 2 
at 18, according to the time elapsed after solution, by the specific 
conductivity. 



After 5 minutes 
1 10 
' 1 hour 
' 3.5 

5 

6 

' 24 
' 48 
' 72 

1 168 .. 
' boiling 

72 hours later 



-5 -1 -1 
1469 X 10 ohm c.c. 
1556 
1867 
1965 
1980 
1989 
2024 
2071 
2104 
2107 
2777 
2722 



This increase in conductivity is due of course to the hydrochloric 
acid liberated. The change is rapid in the first sixty minutes at an 
average rate of 67 X 10' 5 ohm" 1 c.c.' 1 per minute. For the next 168 
hours it is nearly stationary, averaging 0.014 X 10" 5 ohm' 1 c.c." 1 per 
minute, indicating the formation of a more stable basic chloride 
which breaks down under the influence of heat with a rapid increase 
of more than 30 p.c. in conductivity. At this point the liberation of 
hydrochloric acid seems to come to an end and a slow reversal is 
shown, doubtless due to the gradual escape of the freed acid or partial 



COMPOUNDS WITH HALOGENS 69 

recombination. When ionized in solution the zirconyl radical forms 
the cation. In a 2 p.c. solution of zirconyl chloride in half-normal 
hydrochloric acid (time 14 hours, current 0.05 amp.) 0.0280 grams of 
Zr0 2 were found in the cathode arm and 0.0005 grams in the anode. 

In the course of the hydrolysis and under varying conditions of 
temperature and concentration certain definite basic zirconyl chlo- 
rides are formed. The first of these is Zr 2 3 Cl 2 (on water-free basis) 
as described by Endemann (209). It may be precipitated from an 
alcoholic solution of zirconyl chloride by the addition of ether and, 
as Chauvenet (122) has shown, retains three molecules of water. 
More properly then the formula may be written ZrO(OH) 2 ZrOCl 2 . 
It can be prepared (122) in the water-free condition by heating the 
hydrate ZrOCl 2 .2H,0 to 230 under hydrogen chloride. This basic 
chloride is soluble in water and may be transformed into ZrOCl 2 by 
adding concentrated hydrochloric acid and warming. At 300 the 
water-free ZrOCl 2 and Zr 2 3 Cl 2 dissociate into ZrCl 4 and Zr0 2 . Ende- 
mann reported also a basic zirconyl chloride with the composition 
Zr 3 4 Cl 2 , the existence of which has not been confirmed. When zir- 
conyl chloride or the basic chlorides are heated to a high temperature 
a small portion of the chlorine is retained even after prolonged heating 
at 1000. The hydrolysis of zirconyl chloride at and 20 has been 
measured by Venable and Jackson (749) . 

In dialyzing zirconyl chloride, Ruer (618) found that a hydrosol 
with a lower ratio than Zr0 2 : Cl : : 0.2958 : 0.0060 was not obtainable. 
This chlorine could not be separated by silver nitrate except after 
treatment with nitric acid. A gel of zirconyl hydroxide separated in 
the dialysis. The hydrosol contained colloidal hydroxide which could 
be freed from the small amount of chlorine by adding first silver 
nitrate in the proper amount, then nitric acid, and warming or agitat- 
ing. By evaporating a dilute solution of zirconyl chloride to a very 
small volume, diluting and evaporating again three or four times, most 
of the hydrochloric acid liberated on hydrolysis was driven off, Ruer 
(619). The liquid became opalescent and finally milky. The final 
evaporation left about 15 c.c. A very finely divided precipitate set- 
tled out, leaving a liquid in which very little zirconium could be 
detected. Washing with water caused the liquid to become milky once 
more. The precipitate was centrifuged. Concentrated hydrochloric 
acid was added and the centrifuging repeated. Water was added, then 
hydrochloric acid, and the mixture centrifuged, and these operations 
repeated. The yield of precipitate was almost quantitative. It was 



70 ZIRCONIUM AND ITS COMPOUNDS 

dried in vacuo over sulphuric acid and over potassium hydroxide and 
yielded a loose white powder. Four preparations showed this to be 
of practically constant composition. No formula for the substance 
is given by Ruer, but on calculation from his analyses its composition 
corresponds closely with 9ZrO(OH) 2 .ZrOCl 2 . aq. It was only par- 
tially dried when heated to 130, losing almost no hydrochloric acid, 
showing that part of the water is very firmly held. This compound 
Ruer (619) called metazirconic chloride. It is really a highly hydro- 
lyzed basic chloride and on the water-free basis might be represented 
by the formula Zr 10 19 Cl 2 . The formula given above goes to show 
that out of 10 molecules of zirconyl chloride 9 had undergone hydrol- 
ysis. This substance before drying is soluble in water. On dialyzing 
this solution a colloidal solution containing less than 1 p.c. of chlorine 
is obtained; hence it is a solution of nearly pure zirconyl hydroxide 
or metazirconic acid. It is difficult to transform this basic chloride 
into zirconyl chloride by the action of hydrochloric acid after once 
removing the excess of water. After boiling five grams with a half- 
liter of concentrated hydrochloric acid for three hours only 20 p.c. 
had been changed. For complete change it was necessary to heat it 
with one kilo for thirty hours. 

By dissolving zirconium hydroxide in hydrochloric acid, concen- 
trating, and crystallizing it has been claimed (247) that a crystalline 
mixture of ZrOCl 2 .8H 2 O and Zr 5 8 Cl 2 .22H 2 is obtained. It is 
stated that this new basic chloride can be separated from hydrochloric 
acid by recrystallization. The existence of this salt with its peculiar 
behavior lacks confirmation. The existence of a basic chloride 
Zr 4 2 Cl 6 , which Troost and Hautefeuille (716) reported as formed 
when ZrCl 4 was heated in a stream of oxygen, has been shown by 
Chauvenet (122) to be an error. If the oxygen is not thoroughly 
dried a small amount of the tetrachloride is hydrolyzed to zirconyl 
chloride, which breaks up on heating into zirconia and chlorine. This 
zirconia in small amounts may be entrained in the vapor of the tetra- 
chloride. In larger amounts its presence is shown by its insolubility. 

Double compounds. Nilson (518) on mixing a solution of 
ZrOCl 2 .8H 2 with chloroplatinic acid, H 2 PtCl 6 , obtained crystals in 
the form of small, clear, yellow prisms. They were fairly stable in 
the air. The melting point was 100. One-half the water was lost 
at this temperature, giving a shellac-like mass. The composition is 
represented by the formula ZrOCl 2 .PtCl 4 .12H 2 0. Also a compound 



COMPOUNDS WITH HALOGENS 71 

was obtained with platinous chloride which had the composition 
ZrOCl 2 .PtCl 2 .8H 2 0. 

Compounds with Chl-oric Acid. The normal chlorate (ZrC10 3 ) 4 
has probably not been prepared, though Weibull (794) stated that he 
had prepared it by double decomposition according to the equation 
Zr(S0 4 ) 2 + 2Ba(C10 3 ) 2 = Zr(ClO 3 ) 4 +2BaS0 4 . No details or 
analyses are given. This is manifestly erroneous, since both zirco- 
nium sulphate and chlorate are hydrolyzed in aqueous solution. A 
basic zirconyl chlorate has been prepared by Venable and Smithey 
(751) by adding a solution of potassium chlorate to a cold solution 
of zirconium perchlorate, crystallizing out the potassium perchlorate, 
and allowing the basic zirconyl chlorate to crystallize over phosphorus 
pentoxide. It forms fairly large, distinct crystals which were very 
deliquescent and could not be dried over sulphuric acid or calcium 
chloride. They were soluble in alcohol but not in ether. These crys- 
tals oxidize organic matter and are slightly yellowish in color from 
partial decomposition, chloric acid being liberated with the formation 
of chlorine dioxide. The composition of the crystals agrees with the 
formula ZrO(OH) 2 .3ZrO(C10 3 ) 2 . 

Compounds with Perchloric Acid. The normal zirconyl perchlo- 
rate has not been prepared. An acid perchlorate or zirconyl perchloric 
acid has, however, been prepared by Venable and Smithey (751) by 
dissolving the hydroxide in perchloric acid at ordinary temperature 
in the presence of an excess of hydroxide. It forms large crystals of 
the triclinic system, which explode when sharply heated. The anal- 
yses correspond with the formula 4ZrO(C10 4 ) 2 .C10 4 H. 

When the perchloric acid was saturated with zirconyl hydroxide 
by heating on a water bath with excess of hydroxide radiating clusters 
of crystals were formed from which single crystals could not well 
be separated. These were very deliquescent, soluble in alcohol, ether, 
benzene, chloroform, and carbon tetrachloride, but no crystals were 
obtained from these solutions. A small portion, heated rapidly on 
platinum, exploded with a sharp report. Decomposition was evident 
at 100. Slowly heated they intumesced and finally left a white 
powder of zirconia. Several preparations were made. The analyses 
correspond with the formula ZrO(OH) 2 .9ZrO(C10J 2 . One molecule 
of the zirconyl perchloric acid therefore seems to dissolve one mole- 
cule of zirconyl hydroxide, giving a compound in which the ratio of 
zirconyl hydroxide to zirconyl perchlorate is 1 : 9. On recrystallizing 



72 ZIRCONIUM AND ITS COMPOUNDS 

this product it is dissociated and the original zirconyl perchloric acid 
formed (751). 

Zirconium and Bromine 

Zirconium Tetrabromide (ZrBr 4 ). This has been prepared (480) 
by passing carbon dioxide saturated with bromine vapors over a mix- 
ture of zirconia and charcoal heated to a bright red "heat. It forms 
a white, crystalline powder which can be volatilized without decom- 
position. It is not reduced by hydrogen at a white heat but is decom- 
posed by moist air and reacts energetically with water, yielding a 
solution of zirconyl bromide. It has also been prepared by passing 
bromine vapors over heated zirconium (22) or the carbide (674). 
Here, also, a stream of "carbon dioxide may be used as the carrier. 
It is very hygroscopic, giving off hydrobromic acid. It is soluble 
in alcohol or ether. 

The tetrabromide forms compounds with ammonia in a manner 
similar to the tetrachloride. Thus, when saturated with ammonia 
passing over it at 16 it. forms the compound ZrBr 4 .10NH 3 (674). 
This is a very hygroscopic white powder, giving off ammonia. If 
warmed (472) it forms a somewhat more stable compound ZrBr 4 .4NH 3 , 
which on heating gives the nitride and by further heating in hydrogen 
yields the metal. With ethylamine the compound ZrBr 4 .4C 2 H 5 NH 2 
is formed; with anilin, ZrBr 4 .4C 6 H 5 NH 2 ; and with pyridin 
ZrBr 4 .2C 5 H 5 N, showing the same power of forming addition com- 
pounds with organic bases that the tetrachloride has. Rosenheim 
and Frank (609), by the addition of pyridin and chinolin to a solu- 
tion of hydrogen bromide in alcohol saturated with zirconium hydrox- 
ide, obtained the compounds (C 5 H 5 N) 2 H 2 ZrBr 6 and (C 9 H 7 N) 2 H 2 ZrBr 6 . 

Zirconyl Bromide (ZrOBr 2 ). This can be prepared by dissolving 
zirconyl hydroxide in hydrobromic acid and allowing the solution to 
evaporate to crystallization. It can also be prepared by the hydrol- 
ysis of the tetrabromide in aqueous solution or by dissolving the 
hydroxide in a saturated solution of hydrogen bromide in absolute 
alcohol. The crystals are granular (44) or fine, brilliant, needlelike 
(742), optically uniaxial, tetragonal, and isomorphous with the cor- 
responding zirconyl chloride. The formula usually assigned them is 
ZrOBr 2 .8H 2 0, but it is difficult to remove the surplus water without 
decomposition, so as much as 13 and 14 molecules of water of crys- 
tallization have been reported. The crystals readily lose hydrobromic 
acid in a current of dry air or when placed over a dehydrating agent. 



COMPOUNDS WITH HALOGENS 73 

They are more hygroscopic than the zirconyl chloride crystals, decom- 
posing on exposure to moist air. These crystals are soluble in hot, 
concentrated hydrobromic acid, crystallizing out again on cooling. 
Dried at 100-120 in a rapid stream of hydrogen bromide a hard, 
crystalline solid (742) which is readily soluble in water is obtained. 
This has the composition ZrOBr 2 .4H 2 0. 

Basic Zirconyl Bromide ZrO(OH) 2 .ZrOBr 2 .3H 2 (or 4H 2 0). 
This basic salt (742) was obtained by the prolonged boiling of a satu- 
rated solution of the hydroxide in concentrated hydrobromic acid and 
subsequent evaporation of the solution (deeply colored with 
bromine) on a water bath. White crystals with the composition 
ZrO(OH) 2 .ZrOBr 2 .4H 2 separated out. Gelatinous zirconyl hydrox- 
ide was also distributed through the solution. Another crop of smaller 
needlelike crystals was obtained on further evaporation of the solution. 
These had the composition ZrO(OH) 2 .ZrOBr 2 .3H 2 0. The gelatinous 
hydroxide, retaining some bromine, could be separated as a hydrogel 
by dialysis, the basic zirconyl bromide going into solution. A basic 
zirconyl bromide of a similar composition was obtained also by 
Weibull (795). 

Zirconium and Iodine 

Zirconium Tetraiodide (ZrlJ. Attempts to prepare this salt by 
the action of iodine upon a mixture of zirconia and carbon raised to 
a high temperature have failed (480). Nor was it formed when 
vapors of the tetrabromide were passed over heated potassium iodide 
(480.) Furthermore, iodine seems to have slight direct action upon 
metallic zirconium (22, 480). Hydrogen iodide, however, acts upon 
the metal at 340 or upon the carbide at 490. The reaction is ener- 
getic and a rust-brown sublimate is formed intermixed with iodine 
crystals. No white sublimate was observed by Stahler and Denk 
(673). The excess of iodine was removed by washing with benzene, 
leaving a red-brown residue which appeared as a crystalline powder 
when examined under the microscope. This fumed in the air and 
dissolved in water with energetic reaction. It also reacted energeti- 
cally with alcohol, giving zirconyl hydroxide and ethyl iodide. It is 
slightly soluble in benzene or carbon disulphide and more readily 
soluble in ether, giving a yellow addition product. It is strongly 
hydrolyzed by water and decomposed by strong acids (673). Older 
statements that are apparently irreconcilable with these occur in the 
literature (176). 



74 ZIRCONIUM AND ITS COMPOUNDS 

The possible existence of a periodide, ZrI 4 .I 2 , has been based (674) 
upon the fairly constant proportions observed in the product obtained 
in the preparation of the tetraiodide before the treatment with ben- 
zene. On subliming this product at a temperature over 300 a heavy, 
dark-brown vapor, which condensed to a red-brown powder, was 
formed. 

Addition compounds. Addition compounds are formed by the 
tetraiodide with ammonia. When a stream of dry ammonia is passed 
(674) over crystals of the tetraiodide at a temperature not exceeding 
22 a constant weight is reached at which the composition corresponds 
to the formula ZrI 4 .8NH 3 . This substance, according to Stabler 
and Denk, may be regarded possibly as a double compound of the 
amid and ammonium iodide, and on that basis would be ascribed the 
formula Zr(NH 2 ) 4 .4NH 4 I. Liquid ammonia largely dissolves and 
separates the ammonium iodide. Against this view, however, may 
be considered the gradual loss of ammonia on raising the temperature. 
At 100 the composition is ZrI 4 .7NH 3 ; at 150 it is ZrI 4 .6NH 3 ; 
and up to 200 it is ZrI 4 .4NH 3 . At this temperature decomposition 
begins to take place and ammonium iodide is driven off. Supposedly 
it follows the analogy of the corresponding chlorine and bromine com- 
pounds, and at temperatures over 300 is changed to the nitride which 
may be reduced by heating with hydrogen. The probable formation 
of addition compounds with organic bases has not been investigated. 
Stabler and Denk (674) have prepared a compound with ether which 
has the composition ZrI 4 .4(C 2 H 5 ) 2 0. 

Zirconyl Iodide. The normal salt, ZrOI 2 , has been prepared by 
the hydrolysis of the tetraiodide (674). It crystallizes in colorless 
needles having the composition ZrOI 2 .8H 2 0. These are very hygro- 
scopic and are soluble in water or alcohol. The preparation of this 
salt by dissolving the hydroxide in hydriodic acid presents several 
difficulties (742). Zirconyl hydroxide is scarcely attacked by this 
acid; hence the cold precipitated zirconium hydroxide must be used. 
Even this is only sparingly dissolved. The best results are obtained 
when hydrogen iodide is passed into water in which the hydroxide is 
suspended. The evaporation to the crystallizing point brings about 
decomposition of the hydriodic acid and the crystals formed are col- 
ored with iodine, which is difficult to remove by treatment with ben- 
zene or carbon disulphide. The hydrolysis proceeding during these 
operations brings about the formation of basic salts. 

Basic Zirconyl Iodides. The compound ZrO (OH) 2 ZrOI 2 . 5H 2 



COMPOUNDS WITH HALOGENS 75 

has been prepared by Hinsberg (337) by the double decomposition of 
barium iodide with zirconyl sulphate in solution. It is an amorphous, 
colorless powder which decomposes in the air, becoming colored with 
iodine. It is soluble in water. A still more basic substance was 
obtained by Venable and Baskerville (742) by the action of hydriodic 
acid upon zirconium hydroxide suspended in water and the evapora- 
tion of the solution. To limit the decomposition and separation of 
iodine this evaporation may be carried out in an atmosphere of 
carbon dioxide, in which case the salt ZrOI 2 .8H 2 is obtained (674). 
Ordinary evaporation gave a hard, hornlike, colored mass. 

Zirconyl lodate. The normal salt, ZrI0 3 , has not been prepared. 
Basic iodates are formed (751) when a solution of iodic acid is added 
to a solution of zirconyl chloride. The white precipitate is quite 
insoluble in water or dilute nitric acid; hence the precipitation is prac- 
tically complete, and this has been recommended as a means of sepa- 
ration for zirconium analytically. A series of basic zirconyl iodates 
are formed according to the concentration of the solutions used, the 
temperature, and the extent of the washing of the precipitate. 

Zirconyl Periodate. This substance has been prepared by Weibull 
(794) as a white precipitate, insoluble in water, by adding a solution 
of periodic acid to one of zirconyl chloride. No details are given as 
to composition. 



Chapter V 

Compounds with the Acids of Sulphur and Selenium 
Compounds Formed with Sulphurous Acid 

Zirconium Sulphite Zr(S0 3 ) 2 .7H 2 0. This has been prepared 
(740) by suspending the hydroxide in water and saturating with 
sulphur dioxide, separating the insoluble basic salts formed, and 
allowing the solution to evaporate to less than one-twentieth of its 
bulk over sulphuric acid. Hard, white, warty crystals attached them- 
selves firmly to the sides of the dish. The analysis showed their 
composition to correspond with the above formula. 

Basic Zirconyl Sulphites. Several basic salts have been reported. 
Hermann (320) found that ammonium sulphite gave a basic precipi- 
tate when added to a solution of a zirconium salt. This was soluble 
in an excess of the ammonium sulphite. Zirconium hydroxide was not 
precipitated from this solution by alkalies while cold, but a precipitate 
formed on boiling. The formation of a precipitate on passing sulphur 
dioxide into a solution of a zirconyl salt was also observed by Ber- 
thier (43). This precipitate is not readily formed if zirconyl sulphate 
is used, even after boiling (740). It forms readily when a nearly 
neutral solution of zirconyl chloride is used; especially after boiling. 
This precipitate varies in composition, the ratios of zirconia to sul- 
phur dioxide in several preparations ranging from 2 : 1 to 4 : 1, show- 
ing an excess of base. 

The precipitation of zirconium by means of sulphur dioxide is not, 
under ordinary conditions, complete nor does it bring about a complete 
separation from iron, for which purpose it has been recommended, 
but for many purposes the degree of elimination of iron is satis- 
factory. 

Zirconyl Thiosulphate. Sodium thiosulphate forms a precipitate 
when added to a neutral solution of the chloride (686). A partial 
investigation of this (740) showed that the precipitate varied in com- 
position according to the extent of hydrolysis and consisted of basic 
forms of zirconyl thiosulphate. 

76 



COMPOUNDS WITH THE ACIDS OF SULPHUR 77 

Compounds with Sulphuric Acid 

Normal Zirconium Sulphate (Zr(SOJ 2 ). This salt was first pre- 
pared by Berzelius (53) by heating zirconia with an excess of con- 
centrated sulphuric acid and driving off the excess of sulphuric acid 
below a red heat. He reported it as stable up to a low red heat but 
stated that it decomposed at higher temperatures, also that it crys- 
tallized from H 2 S0 4 but better from water. Undoubtedly a red heat 
is too high, and some of the combined acid was driven off. Other 
investigators (22, 293, 795) have shown that lower temperatures must 
be used for driving off the excess of acid, the range being 350-400. 
Hauser (293) prepared the sulphate by treating incompletely dried 
zirconia, which dissolves more readily, with concentrated acid and 
then driving off the excess acid at 360-380. This may be done 
conveniently in a Kjeldahl flask over which is fitted a small funnel 
connected with a suction pump for carrying off the fumes and pre- 
venting the access of dust. Dried zirconia is acted upon slowly and 
with difficulty, and ignited zirconia is scarcely attacked at all. The 
salt is quite stable and only traces of the combined acid are lost after 
heating at 380 for eight to ten hours. If a gas burner is used for 
the heating the product must be protected from the water formed in 
the combustion of the gas, as this partially hydrolyzes the sulphate. 

The neutral water-free sulphate dissolves slowly in water, evolv- 
ing a considerable amount of heat. This Hauser (293) attributed to the 
formation of the tetrahydrate, Zr(S0 4 ) 2 + 4H 2 = Zr(SOJ 2 .4H 2 O, 
which then dissolves without heat evolution but is hydrolyzed to 
zirconyl sulphate. The heat of formation from the action of sul- 
phuric acid upon the hydroxide is given by Pissarjewski (554) as 
11,670 cal. The tetrahydrate Zr(SOJ 2 .4H 2 forms rhombic or small 
tabular crystals. It is insoluble in alcohol. Three molecules of 
water are lost on heating at 100-120, the fourth only on prolonged 
heating at a higher temperature short of decomposition (536, 610). 
On slow concentration of a solution of zirconium sulphate containing 
an excess of sulphuric acid a crystalline crust is formed. This retains 
water of crystallization. When an aqueous solution to which no 
acid has been added is evaporated the hydrolysis is far-reaching and 
a gumlike mass is left. Sulphur trioxide is driven off on ignition of 
the sulphate, but heating for some time at a temperature of 900- 
1000 fails to remove the last traces. Bailey (22) heated it with 
ammonium carbonate in order to remove the last of the sulphur tri- 



78 ZIRCONIUM AND ITS COMPOUNDS 

oxide but according to other investigators this involved the loss of 
some zirconia. The anhydrid 2ZrO.S0 3 is left when the sulphate is 
heated for some time at 200-300 in the presence of water vapor. 
This is commonly found in commercial preparations of the sulphate. 

The normal zirconium sulphate is readily hydrolyzed when dis- 
solved in water, giving a strong acid reaction. The extent of this 
hydrolysis depends upon the extent of the dilution, the time elapsed, 
and the temperature. For instance, the specific conductivity of a 
1.75 p.c. solution at 18 when determined immediately after prepara- 
tion was found by Ruer and Levin (621) to be 3105X10' 5 ohmXc.c.- 1 . 
After twenty hours it was 3186; after boiling 3418. Twenty-four 
hours later it was 3432 and this had not changed after standing 
seventy-two hours. Very dilute solutions become opalescent on boil- 
ing and the hydroxide separates. These 'become clear again on con- 
centration. The work of Venable and Jackson (750) would indicate 
that on dissolving the normal sulphate Zr(S0 4 ) 2 at and also at 
20 there was for the first three observations taken at 5-minute 
intervals a slight increase of resistance followed by a slow decrease 
for three hours. After that an equilibrium was reached. The be- 
havior in the first 15 minutes was doubtless due to change in reach- 
ing a temperature equilibrium. The addition of alcohol to solutions 
of the normal sulphate causes the precipitation of basic zirconyl salts. 
Crystalline basic salts also form under certain conditions of dilution 
and temperature (295) and the boiling of dilute solutions gives pre- 
cipitates of basic compounds (601). 

Acid Sulphates or Zircon-Sulphuric Acid. The existence of such 
compounds for the normal sulphate has been questioned but seems 
probable. The subject was brought under investigation by the dif- 
ference shown by the sulphate from certain other zirconium salts in 
its behavior towards various reagents, such as oxalic acid or am- 
monium oxalate. This has been studied by a number of investigators 
and several theories have been formulated as to the constitution of 
the sulphate when dissolved. Hauser (296) found that the solubility 
of the sulphate in H 2 S0 4 decreased with the increase of concentration 
of the acid up to a certain point and then suddenly and notably in- 
creased to a point at which a slightly increased concentration de- 
creased the rate of solution. By using a concentration greater than 
61.4 p.c. there may be obtained a clear liquid which, on standing a 
number of days, deposits fine, monoclinic, needlelike crystals quite dif- 
ferent in form from those of the salt Zr(S0 4 ) 2 .4H 2 0. The analysis cor- 



COMPOUNDS WITH THE ACIDS OF SULPHUR 79 

responded to the composition Zr(SO 4 ) 2 .H 2 S0 4 .3H 2 O. The formation 
of these crystals is easy to overlook as they crystallize slowly. The 
exact conditions for their formation are as follows: The tetrahydrate, 
Zr(S0 4 ) 2 .4H 2 0, is practically insoluble in water containing 45-55 p.c. 
of S0 3 ; with more than 57 p.c. there is a rapid increase in solu- 
bility. The reaction, as stated by Hauser, Zr(SOJ 2 .4H 2 0^ 
Zr(S0 4 ) 2 .H 2 S0 4 .3H 2 0, takes place at 39.5 and a concentration of 
61.4 p.c. S0 3 . On melting this trihydrate with much concentrated 
H 2 S0 4 in a glass tube and allowing it to stand for some days a com- 
pact, crystalline powder, which on analysis gave the monohydrate 
Zr(SO 4 ) 2 .H 2 S0 4 .H 2 O, is formed. These hydrates Hauser called hy- 
drates of zircon-sulphuric acid, Zr(SO 4 ) 2 .H 2 S0 4 . He also noted that 
the boiling points of solutions of Zr(S0 4 ) 2 .4H 2 in concentrated 
H 2 S0 4 slowly but materially fall on heating, and basic zirconyl salts 
separate as crystals or precipitates. In the electrolysis of this zircon- 
sulphuric acid the zirconium formed a complex anion. Thus 

H 2 [Zr(S0 4 )] 3 * 2H, Zr(S0 4 ) 3 . The behavior under electrolysis 
would manifestly depend largely upon the dilution, and the presence 
of water brings about hydrolysis. It is quite possible, therefore, for 
the solid salt to be zirconium bisulphate. Double salts have been 
obtained with the alkaline sulphates. 

Ruer (617) in his investigation of the constitution of zirconium 
sulphate tetrahydrate reached the conclusion that in aqueous solution 
the formula should be ZrOS0 4 .H 2 S0 4 , which undergoes a progressive 
further hydrolysis unless excess of acid is present. Further, he con- 
tended that in the crystalline form the constitution is to be expressed 
by the formula ZrOS0 4 .H 2 S0 4 .3H 2 O. He found the electrical dis- 
sociation in solution to be ZrOSO 4 . H 2 SO 4 <= 2H, ZrO(S0 4 ) 2 , the 
zirconium migrating with the negative stream. Double salts with 
sodium, as Na 2 S0 4 . ZrOSO 4 , dissociate in the same way. It has been 
shown also that the supposed ZrS0 4 .4H 2 O loses three molecules of 
water at 100, the fourth molecule being lost only after prolonged 
heating at a higher temperature, indicating the absorption of energy 
in the dissociation of the molecule and re-formation of water. Chau- 
venet and Gueylard (134) found that cryoscopic measurements gave 
the molecular weight of the sulphate in solution as 79.4 instead of 
286.6, or approximately four independent particles to the molecule. 
Analysis gave the probable form as ZrOS0 4 .H 2 S0 4 . Conductivity 



80 ZIRCONIUM AND ITS COMPOUNDS 

experiments during neutralization with NaOH indicated the presence 
of three compounds, ZrOS0 4 , ZrOS0 4 .Zr0 2 , and 3ZrOS0 4 .Zr0 2 . 

The addition of alcohol to the solution of the sulphate gives basic 
precipitates. The objection may be raised here that the alcohol 
itself has a hydrolyzing effect. The use of ether, which is not open 
to this objection, also yields strongly basic compounds. Rosenheim 
and Frank (609) assumed, on the basis of their experiments, the 
existence of an equilibrium 2ZrO(S0 4 H) 2 + H 2 ^Zr 2 3 (S0 4 H) 2 
+ 2H 2 S0 4 . Other work bearing on this subject may be found in 
references 568, 570, 38, 561. 

The mass of evidence would go to show that zirconium sulphate, 
Zr(S0 4 ) 2 , exists only in the entire absence of water. The normal sul- 
phate dissolves slowly in water. Attempts at making a one-fifth 
molar solution at left a portion undissolved, but the one-tenth 
molar was made, evolving considerable heat and requiring some 15 
minutes for temperature adjustment (750). The hydrolysis then 
progresses, reaching apparently an equilibrium after 3-4 hours, or 
at least a point at which the velocity of reaction is very slight. The 
velocity also diminishes with decreasing temperature. Basic salts 
may settle out and these will be described under that heading (296). 
The normal sulphate crystallizes from concentrated H 2 S0 4 without 
change. With a concentration of 50-60 p.c. S0 3 the bisulphate 
crystallizes. Below that concentration zirconyl acid sulphate, 
ZrOSO 4 .H 2 S0 4 ..3H 2 0, is obtained in crystalline form. With still 
greater dilution crystalline basic zirconyl salts are formed. 

Double Salts of Zirconium Sulphate with the Alkaline Sulphates. 
Rosenheim and Pinksker (612) have reported that normally consti- 
tuted double alkali sulphates separate from a solution of Zr(S0 4 ) 2 in 
H 2 S0 4 on the addition of solutions of the alkali sulphates. These are 
regarded as derivatives of H 4 (Zr(S0 4 ) 4 ). They may also be looked 
upon as double salts with zirconium bisulphate, K 2 S0 4 ..ZrH 2 (S0 4 ) 3 . 
They undergo hydrolysis in water. 

The normal double sulphate, 2K 2 S0 4 .Zr(S0 4 ) 2 .3H 2 0, which may 
be written as the potassium salt of the above complex acid, is formed 
when potassium bisulphate in concentrated solution and at boiling 
temperature is saturated with Zr(OH) 4 , freshly precipitated in the 
cold (609, 610) . The salt forms in very soluble, needlelike crystals. 
Analogous salts of sodium and ammonium have also been formed. 
When KHS0 4 is added to a solution of Zr(S0 4 ) 2 basic zirconyl sul- 
phates form. 



COMPOUNDS WITH THE ACIDS OF SULPHUR 81 

Zirconyl Sulphate. Berzelius (53), by saturating a solution of 
zirconium sulphate with the hydroxide and evaporating, obtained a 
gumlike mass which became white on drying. On further heating it 
intumesced and lost water. On ignition it lost additional water and 
S0 3 . The analysis gave the ratio Zr0 2 : S0 3 : : 100 : 65.9. The 
original gum could be dissolved in a small amount of water but gave 
a precipitate on the further addition of water. From a similar solu- 
tion -by neutralizing with ammonia Kulka (417) prepared a gela- 
tinous substance having the same composition. The gummy mass 
separated out and was soluble in water but insoluble in acid. Ac- 
cording to the view of Hauser (292), these were to be regarded as 
solutions of the colloidal hydroxide in the neutral sulphate. He 
found that fresh cold-precipitated hydroxide, which is largely 
Zr(OH) 4 , dissolved more easily. Concentrated solutions of the sul- 
phate digested at 60 with this hydroxide for several days gave a 
solution , containing Zr0 2 : S0 3 :: 1.15 : 1. Other investigators have 
reported this ratio as 1 : 1. Much less of the hot-precipitated hydrox- 
ide is dissolved. Zirconyl sulphate was not obtained on evaporating 
this solution. 

Though zirconyl sulphate ZrOS0 4 is doubtless the first stage in 
the hydrolysis of the sulphate, it seems to be quickly converted into 
basic salts and no account of its separation has been given that is 
not open to criticism. As has been already shown, the crystalline 
tetrahydrate ZrS0 4 ) 2 .4H 2 should have assigned to it the formula 
ZrOS0 4 .H 2 S0 4 .3H 2 0, and hence may be regarded as the hydrate of 
a zirconyl sulphuric acid or of the acid zirconyl sulphate whose for- 

H\ 

S0 4 
mula would be ZrO< . This corresponds to zircon-sulphuric acid 

S0 4 
H/ 

H>S0 4 

or acid zirconium sulphate Zr = S0 4 . 

H>S0 4 

Zirconyl sulphate is reported by Chauvenet (130) as water-free 
ZrOS0 4 and in the following hydrates: ZrOS0 4 .4H 2 0; ZrOS0 4 .2H 2 0; 
ZrOS0 4 .H 2 0. The acid sulphate is given as ZrOS0 4 .S0 3 ; 
ZrOS0 4 .S0 3 .H 2 0; ZrOSO 4 .S0 3 .4H 2 0. 

Basic Zirconyl Sulphates. The boiling points of solutions of 
ZrOS0 4 . H 2 S0 4 . 3H 2 in H 2 S0 4 decrease slowly but materially on pro- 
longed heating. This, according to Hauser (296) , is to be referred 



82 ZIRCONIUM AND ITS COMPOUNDS 

to the formation of a basic salt, 2Zr0 2 .3S0 3 .5H 2 0, which separates 
in crystalline form from very concentrated solutions. Less concen- 
trated solutions give a flocculent precipitate on boiling. This deposi- 
tion of crystals causes a fall in temperature. At a definite dilution 
the basic salt, 4Zr0 2 .3S0 3 .14H 2 0, separates, the extent of dilution 
necessary depending upon the temperature. With increase of tem- 
perature a greater dilution becomes necessary and on very great 
dilution no precipitation is observed. The velocity of the reaction 
is slight and diminishes with decreasing temperature so that the solu- 
tion may require prolonged standing for the detection of the deposit. 
It is best observed at a temperature of 39.5. As reported by Hauser, 
the solution remained clear for dilutions Zr(S0 4 ) 2 : H 2 : : 3 : 8.3 : : 
3 : 10 :: 3 : 16, but precipitation began at 3 : 20 and continued up to 
a dilution of 1 : 120 after standing for ten hours at 39.5. The crys- 
talline salt, 4Zr0 2 .3S0 3 .14H 2 0, was therefore not decomposed at 
that temperature and dilution. Its solubility is less than 0.009 p.c. 
It was found that the original salt had been hydrolyzed in this way 
to the extent of 66-67 p.c. of the total. Dilute H 2 S0 4 dissolves this 
salt very slowly, concentrated acid readily. The element of time in 
this change is important, and ranges for dilute solutions from two to 
five days. From these observations it will be seen that the nature 
of a solution of zirconyl sulphate depends largely upon its previous 
history. It may be noted that the formula for this basic salt may 
also be written ZrO(OH) 2 .3ZrOS0 4 .13H 2 in agreement with the 
analysis and also with the fact that very dilute solutions are opales- 
cent and yield the colloidal hydroxide ZrO(OH) 2 on being dialyzed. 
Very dilute solutions of this basic sulphate which have been heated 
for a time at 64 have lost the power of forming the crystalline deposit 
when allowed to stand at a lower temperature. They also show 
analytical differences. No immediate precipitate is given with H 2 2 
but only after standing. Oxalic acid in small amount also gives 
none. The formation of this indifferent stage seemed to depend in 
large measure upon the concentration. Concentrated solutions after 
being heated and then diluted behaved differently from those which 
were first diluted and then heated (296) . 

A basic salt, 2Zr0 2 . 3S0 3 . 5H 2 0, crystallized from very concen- 
trated solutions and a flocculent precipitate, doubtless without defi- 
nite composition, separated from quite dilute solutions. This latter 
is very slightly soluble in water, giving a weakly acid reaction. It 
is slowly dissolved in dilute H 2 S0 4 but rapidly dissolved when the 



COMPOUNDS WITH THE ACIDS OF SULPHUR 83 

acid has a 30 p.c. concentration. On drying at 300 the composition 
was 2Zr0 2 .3S0 3 , Hauser (293). 

According to Berzelius (53), a flocculent basic substance with the 
composition 3Zr0 2 .2S0 3 is formed when alcohol is added to a solu- 
tion of the sulphate. Paykull (536) prepared a substance having a 
similar composition as a fine-grained precipitate by considerably 
diluting the solution and washing the precipitate with boiling water. 
This was insoluble in water and soluble in hydrochloric acid, and was 
hydrated. The formula was calculated on the dry basis. Endemann 
(209) using alcohol as a precipitant and very concentrated aqueous 
solutions of the sulphate, prepared a basic substance having the com- 
position 7Zr0 2 . 6S0 3 . 14H 2 0, which retained some of the alcohol. The 
addition of very little water freed the alcohol; more cold water dis- 
solved the precipitate ; and on driving off the water an amorphous mass 
was left. If much water was used in dissolving an insoluble basic salt 
separated. There is little evidence that these compounds were not 
mere mixtures. 

Chauvenet (128, 130), by determining the densities in nitrobenzene 
at 12.4, obtained a curve with composition and density as the coordi- 
nates. This gave six points of inflection corresponding to the basic 
salts Zr(S0 4 ) 2 ; Zr(S0 4 ) 2 .Zr0 2 ; 5Zr(S0 4 ) 2 .7Zr0 2 ; 3Zr(S0 4 ) .5Zr0 2 ; 
Zr(S0 4 ) 2 .3Zr0 2 ; and Zr(SOJ 2 .2Zr0 2 . 

Patents have been issued for methods of preparation of a basic 
sulphate 5Zr0 2 .2S0 3 .14H 2 (608) and also one having the composi- 
tion 5Zr0 2 . 3S0 3 . 13H 2 0. 

Hauser and Herzfeld (300) have ascribed the following hypo- 
thetical formulas to the basic sulphates obtained by them. One com- 
pound crystallized in needles having parallel extinction. The com- 
position was Zr 4 (S0 4 ) 3 (OH) 10 .10H 2 0. Another compound obtained 
in spheroidal crystals had the formula [ZrJS0 4 ) 2 (OH) 11 ] 2 .S0 4 .8H 2 
assigned to it. Also there were the compounds 

[Zr 4 (S0 4 ) 6 (OH) 6 ]H 4 .4H 2 and [Zr 4 (S0 4 ) 5 (OH) 8 ]H 2 . 
The only double compound prepared in a pure form was obtained by 
dissolving Zr(S0 4 ) 2 .10H 2 in 15 c.c. of water, adding 1 c.c. of con- 
centrated H 2 S0 4 , and then adding dropwise, without stirring, a con- 
centrated solution of K 2 S0 4 until the original precipitate almost dis- 
appeared, leaving a cloudy liquid. The formula assigned the crystal- 
line deposit was K 2 Zr 4 (S0 4 ) 5 (OH) 8 . 

Double Salts of Zirconyl Sulphate with the Alkali Sulphates. 
When potassium sulphate, either in crystals or in saturated solution, 



84 ZIRCONIUM AND ITS COMPOUNDS 

is added in excess to a solution of zirconyl sulphate all of the zir- 
conium is gradually precipitated as a crystalline double salt of vary- 
ing composition. The excess of the potassium sulphate remaining 
in the solution is changed partly into the bisulphate. The composi- 
tion of the basic double salt depends upon the extent to which the 
hydrolysis of the zirconyl sulphate had gone and also upon other 
conditions. Such basic precipitates are formed also on the addition 
of other salts of potassium. These crystalline precipitates are diffi- 
cultly soluble in water and may be reprecipitated by the addition of 
K 2 S0 4 . They are fairly soluble in acids if they have been only 
slightly washed in water. If thoroughly washed they become prac- 
tically insoluble in water or dilute acid. These basic double sulphates 
are decomposed by ammonia and are soluble in ammonium carbonate. 
By washing with water they are separated into a soluble substance 
richer in sulphuric acid and an insoluble one that is poorer. The 
solution of the former forms an abundant crystalline precipitate after 
standing a few days (760). 

Rosenheim and Frank (609) prepared certain double salts with 
alkali sulphates which, they stated, might be regarded as alkali salts 
of a basic zirconyl sulphuric acid, Zr 2 3 (S0 4 H) 2 . These were ob- 
tained by precipitating cold concentrated solutions of Zr(S0 4 ) 2 and an 
alkali sulphate with alcohol and washing with a little alcohol and 
ether. The product was quite homogeneous and consisted of very 
small, probably tabular crystals. They could not be recrystallized but 
suffered change on treatment with water. The following double 
salts were prepared: Zr 2 3 (S0 4 K) 2 .8H 2 0; Zr 2 3 (S0 4 Rb) 2 .15H 2 0; 
Zr 2 3 (S0 4 Cs) 2 .llH 2 0. No analogous salts were obtained with 
sodium and ammonium salts but amorphous basic products only. 
These salts presuppose the existence of a complex anion Zr 2 3 (S0 4 ) 2 . 
Hauser and Herzfeld (300) have denied the accuracy of Ruer's work 
(621) and the existence of the complex anions ZrO(S0 4 ) 2 and 
Zr 2 3 (S0 4 ) 2 . 

According to Chauvenet and Gueylard (134), evidence was ob- 
tained by cryoscopic and thermochemical methods of the existence 
of the following double compounds: 2ZrOS0 4 .S0 3 .3Na 2 S0 4 .8H 2 0; 
3ZrOS0 4 . S0 3 . 2Na 2 S0 4 . 7H 2 ; ZrOS0 4 . S0 3 . (NH 4 ) 2 S0 4 . 3H 2 ; and 
ZrOS0 4 .S0 3 .2(NH 4 ) 2 S0 4 .3H 2 O. Also the following: 3ZrOS0 4 .2M 2 S0 4 
and 3ZrOS0 4 ..M 2 S0 4 where M represents K, Na or NH 4 . 

The complex and varying products obtained by mixing a solution 
of zirconyl sulphate with one of potassium sulphate have long been 



COMPOUNDS WITH THE ACIDS OF SULPHUR 85 

a puzzle. In part, at least, mixtures of hydrolyzed substances are 
formed. Recently it has been shown (298) that if the mixed solu- 
tions are concentrated over sulphuric acid definite compounds crys- 
tallize. These show very well the influence of such a salt as potas- 
sium sulphate upon a progressing hydrolysis. When potassium sul- 
phate is used micro-crystalline needles whose composition is 
K 4 Zr 4 (OH) 8 (S0 4 ) 5 .8H 2 are obtained. In a solution strongly acid 
with sulphuric acid the first crystals formed are K 4 Zr(S0 4 ) 4 ; in 
weakly acid solutions the composition is that of potassium zirconium 
hydroxysulphate of varying composition. These products hydrolyze 
on being treated with water. If boiled with water, they become 
opalescent with colloidal zirconium hydroxide. Following the crystal- 
lizations in detail, the above-mentioned potassium zirconium hydroxy- 
sulphate, K 4 Zr 4 (OH) 8 (S0 4 ) 5 .8H 2 0, forms a crystalline crust of 
needles. A second crop of prismatic crystals is formed and these 
have the composition K 4 Zr(S0 4 ) 4 .5H 2 0. The first crystals hydro- 
lyze to increase the free acid and bring about an equilibrium. The 
formation of the second then begins and decreases the amount of 
free acid. The reaction is thereupon reversed and the hydroxysul- 
phate crystals form once more. 

Compounds with Selenious Acid 

Zirconium Selenite. According to Berzelius (52) this is a white 
powder soluble in an excess of selenious acid. The basic zirconyl 
selenite, 4Zr0 2 .3Se0 2 .18H 2 0, was prepared by Nilson (517) by pre- 
cipitating a solution of zirconyl chloride with sodium selenite. Kulka 
(417) claimed to have prepared the same salt by adding a solution 
of selenium dioxide in nitric acid to a solution of Zr(SOJ 2 . It was 
described as a jelly like precipitate soluble in hydrochloric acid. At 
100 it lost fifteen molecules of water. Weibull (795) found this 
precipitate to have on drying the composition Zr0 2 . Se0 2 . 2H 2 0. 

The normal selenite Zr(Se0 3 ) 2 is reported by Nilson (517) as 
being formed when the above basic salt, 4Zr0 2 .3Se0 2 .18H 2 0, is 
digested with selenious acid at 60. The amorphous or colloidal pre- 
cipitate is changed into microscopic crystals in the form of four-sided 
columns with sharply cut ends. This form is retained when they are 
heated to a temperature at which the selenium dioxide is driven off. 
They are difficultly soluble in hot hydrochloric acid, some of the 
selenium being volatilized as chloride. If a concentrated solution of 



86 ZIRCONIUM AND ITS COMPOUNDS 

selenium dioxide is used the crystals are water-free and have the 
composition Zr(Se0 3 ) 2 . With a more dilute solution one molecule 
of water of crystallization is present, Zr(Se0 3 ) 2 .H 2 0. This is prob- 
ably a zirconyl salt following the analogy of the sulphite. 

Selenious acid has been recommended by Smith and Jones (664) 
as a means of separating and determining zirconium. 

Compounds with Selenic Acid 

Zirconium Selenate. This salt has been obtained by Weibull 
(795) as the tetrahydrate having the formula Zr(SeOJ 2 .4H 2 0, thus 
corresponding to the normal sulphate and probably being hydrolyzed 
in the same way. It was prepared by dissolving zirconium hydroxide 
in selenic acid. It crystallized in transparent four and six-sided 
tables of the hexagonal system. Three molecules of water are lost 
at 100, the fourth between 120 and 130. The water-free salt is 
only slightly hygroscopic. It is soluble in water but only slightly 
soluble in concentrated acids or alcohol. Weibull also obtained basic 
products by hydrolyzing the normal salt with boiling water. 

Compounds with the Oxy acids of Tellurium 

The compounds with these acids have been investigated only by 
Berzelius (59, 60). He reported the tellurite as a white, flocculent 
precipitate and the tellurate as a bulky, semi-transparent mass solu- 
ble in an excess of the zirconyl chloride solution from which it was 
prepared. The method of preparation was by the addition of a 
solution of sodium tellurite or, respectively, the tellurate to the solu- 
tion of a zirconium salt such as the chloride. 



Chapter VI 

Compounds with Acids of the Nitrogen Group and Eare 

Inorganic Acids 

Compounds with Nitric Acid 

Berzelius (52) observed that a solution of zirconium hydroxide 
in nitric acid left on evaporation a yellow gummy mass which lost 
its acid radical on heating. If the heating was not carried beyond 
100 the residue was completely soluble in water and the solution 
had the capacity of taking up still more hydroxide or could be neu- 
tralized with much alkali before a permanent precipitate was formed. 
Mandl (466) failed to prepare a neutral salt by the concentration of 
such a solution or a double salt by adding potassium nitrate. Miiller 
(512) found no nitrate of constant composition but obtained always 
a mixture of the nitrate and the hydroxide formed during the hydrol- 
ysis, this hydroxide going into colloidal solution. Rosenheim and 
Frank (610) could obtain only zirconyl nitrate, ZrO(N0 3 ) 2 .2H 2 0, 
which crystallized in well-defined forms. These, reduced to a fine 
powder, were dissolved by prolonged boiling in absolute alcohol, and 
from this solution ether precipitated a white powder. This was easily 
soluble in water and had the composition Zr 2 3 (N0 3 ) 2 .5H 2 or 
ZrO(OH) 2 .ZrO(N0 3 ) 2 .4H 2 0. Other observations reported by Her- 
mann (320), Paykull (537), and Weibull (794) are manifestly errone- 
ous from a failure to take into account the changes brought about 
by hydrolysis in the solutions. The zirconium nitrate of commerce 
is more or less basic zirconyl nitrate. 

Chauvenet and Nicolle (135) have repeated some of these earlier 
experiments. The concentration of a solution of zirconium hydroxide 
in nitric acid over caustic potash did not yield the normal nitrate, 
nor did the evaporation of a syrupy solution at a low temperature 
in a current of carbon dioxide charged with oxides of nitrogen. The 
latter yielded only zirconyl nitrate. They concluded that the exist- 
ence of the normal nitrate was doubtful. Certainly, if formed, it is 
most easily and rapidly hydrolyzed. They found that the methods 
hitherto used yielded only the zirconyl nitrate which crystallizes with 
two molecules of water. This remains unaltered in the air and does 

87 



88 ZIRCONIUM AND ITS COMPOUNDS 

not fume if entirely freed from adhering nitric acid. Efforts at dehy- 
dration even at the lowest possible temperature and in a current of 
carbon dioxide saturated with oxides of nitrogen failed, as some nitric 
acid always accompanied the water driven off. 

The possible existence of other hydrates was investigated (135) 
by preparing various mixtures of ZrO(N0 3 ) 2 .2H 2 O with water and 
measuring the heat of fixation of n molecules of water to the dihy- 
drate. 

ZrO(N0 3 ) a .2H 2 aq. = ZrO(N0 3 ) 2 diss. + 2.17 cal. 



.3H 2 " 
3.5H 2 O " 
4.17H 2 O " 
4.76H.O " 



0.50 

1.92 

2.77 

3.95 



6H 2 O " = -^5.90 ' 

The curve constructed with these data gave only one angular point 
corresponding to ZrO(N0 3 ) 2 .3.5H 2 0. This hydrate forms at 0, is 
unstable at 10, and effloresces rapidly at ordinary temperature, yield- 
ing the dihydrate. Anhydrous zirconyl nitrate, according to these 
investigators, does not exist. 

The effect of dilution on zirconyl nitrate was also examined (136). 
The dihydrate is very soluble and hydrolyzes immediately. The ex- 
tent of this hydrolysis was measured by conductivity determinations 
on a N/100 solution at 29.5. 

Some minutes after preparation ^505.19 
" hours " " 554. 

" days 600. 

At this point it was apparently constant, remaining stationary for 
some months. There slowly formed a precipitate having the compo- 
sition ZrO(N0 3 ) 2 .Zr0 2 . (H 2 0) n , which may also be written 
ZrO(OH) 2 .ZrO(N0 3 ) 2 .H 2 0) n - 1 . Of course, a number of reactions are 
possible in the changes measured above. An effort was made to deter- 
mine these by neutralizing the liberated acid with N/100 NaOH and 
following up the neutralization by measuring the resistance. Por- 
tions (5 c.c.) of the zirconyl nitrate N/100 solution were taken. The 
results were as follows: 

ZrO(N0 3 ) 2 .2H 2 NaOH W. 

5 257 

5 2 302 

5 4 344 

5 5 373 

5 6 407 

5 7 437 

5 8 470 

5 10 545 

5 12 487 

5 14 411 



COMPOUNDS WITH ACIDS OF NITROGEN GROUP 89 

Examination of the curve constructed from these data indicated the 
presence of two angular points corresponding to the two reactions 
ZrO(N0 3 ) 2 + NaOH = NaNO 3 + ZrONO 3 and ZrO(NO 3 ) 2 +2NaOH 
= 2NaN0 3 + Zr0 2 . From this the inference was drawn that the 
constitution of the zirconyl solution in dissociating was 
Zr(OH) 3 N0 3 .HNO 3 . Cryoscopic measurements gave the molecular 
weight as 92.9 instead of 266.6, which meant that the number of 
independent particles probably numbered three. This is a helpful 
clue toward the solution of the problem, but of course leaves the 
identity of the independent particles unsettled. As to the progressive 
dehydration of the crystals by heat, it was found that dissociation 
began at 120 even in the presence of oxides of nitrogen. At this 
temperature a fairly constant weight can be obtained and the results 
indicated the presence of the basic nitrate Zr0 2 .3ZrO(N0 3 ) 2 , as in 
the case of the sulphate. If dehydrated in air at 110 the substance 
Zr0 9 .2ZrO(N0 3 ) 2 .7H 2 O was left; at 150, 2Zr0 2 .ZrO(N0 3 ) 2 .4H 2 O; 
at 215, 7Zr0 2 .ZrO(N0 3 ) 2 .5H 2 0; at 250, 10ZrO 2 .ZrO(N0 3 ) 2 .4H 2 0; 
and at 300 dissociation was complete with the formation of the end 
product Zr0 2 . 

Wagner (756) has examined what he called the temporary hydrol- 
ysis of zirconyl nitrate solutions with the aid of the ultramicroscope. 
Biltz (68) has dialyzed zirconyl nitrate solutions, finding the outside 
water free from nitric acid after five days and getting a colloidal 
solution of the hydroxide as a hydrosol which was clear in trans- 
mitted and cloudy in reflected light. The colloid was precipitated by 
electrolytes. The Tsigmondy gold number was found to be between 
0.046 and 0.09 with a mean of 0.5. 

Rosenheim and Frank could obtain no double nitrates with the 
alkali nitrates (610) . When ammonia is allowed to act upon zirconyl 
nitrate (ZrO(N0 3 ) 2 .2H 2 0) a white, crystalline mass, scarcely hygro- 
scopic and stable in the air, is obtained. The composition is given 
asZrO(N0 3 ) 2 .2H 2 0.2NH 3 (405). 

Compounds with the Acids of Phosphorus 

On account of the scant and imperfect references in the literature 
it is impossible to give a systematic account of the compounds of zir- 
conium and the zirconyl radical with the various acids of phosphorus. 
Investigations of such possible compounds along modern lines and 
based on a fuller knowledge of their probable behavior are needed. 



90 ZIRCONIUM AND ITS COMPOUNDS 

Wunder and Jeanneret (828) have found that metallic zirconium 
is readily dissolved by a hot solution of phosphoric acid (Sp. Gr. 
1.75). A clear, colorless solution results and whatever carbon was 
present is left undissolved. Further addition of water causes no pre- 
cipitation. No effort to separate or determine the compound formed 
was reported. 

Hautefeuille and Margottet (307) found that zirconium hydroxide 
was dissolved in phosphoric acid heated to a temperature short of 
dehydration and therefore probably in the form of pyrophosphoric 
acid. The amount dissolved was two parts in one hundred of the 
acid. On cooling two varieties of crystals separated from the fused 
mass. These were described as regular octahedra and cubic octa- 
hedra. They had high refractive power but showed no action on 
polarized light. They were not attacked by acids nor by potassium 
bisulphate but were easily decomposed by fusion with alkali car- 
bonates, giving insoluble alkali zirconates which could be obtained 
free from the phosphoric acid. In this fusion the temperature was 
kept as low as possible and the exact equivalent of alkali carbonate 
used. This method of separation was used for the analysis, which 
gave the empirical formula Zr0 2 .P 2 5 . This may be written ZrP 2 7 
and the compound, therefore, is the pyrophosphate. 

Knop (400) fused zirconia with sodium ammonium phosphate at 
a high temperature and for a considerable time. The cooled mass 
was leached with dilute hydrochloric acid. A white powder was 
left which was clearly crystalline under the microscope, the form being 
that of rectangular parallelopideds. They resembled the crystals of 
sodium zirconium phosphate. The analyses are faulty but point to 
the same composition as above, ZrP 2 7 . It is by no means assured 
that these crystals did not contain sodium. 

Weibull (794), making use of precipitation methods, obtained the 
following results: On addition of an aqueous solution of zirconyl 
chloride to an excess of disodium phosphate in solution a finely 
divided white precipitate was formed. This was insoluble in weak 
acids and in an excess of the disodium phosphate. It was slightly 
soluble in hydrochloric acid, more easily soluble in sulphuric acid. 
When dried it was insoluble in acids. By analysis its composition 
was shown to be ZrP 2 7 .2H 2 0. A similar result was obtained by 
dropping a solution of zirconium sulphate into one of disodium pyro- 
phosphate, Na 2 H 2 P 2 7 , the analysis giving the composition as 
ZrP 2 7 .1.5H 2 0. Another experiment in which the solutions of zir- 



COMPOUNDS WITH ACIDS OF NITROGEN GROUP 91 

conyl chloride and sodium phosphate were simply mixed gave a basic 
compound, 5Zr0 2 .3P 2 5 .9H 2 0. Still another carried out in the same 
manner yielded a basic compound 3Zr0 2 . 2P 2 5 . 5H 2 0, and the same 
result was obtained when phosphoric acid was used as the precipi- 
tant. Probably the zirconyl chloride solution used had the same 
previous history as to dilution, time, and temperature. A somewhat 
similar result but differing from the foregoing in the ratio of the com- 
ponents was obtained by the independent investigators, Hermann 
(319) and Paykull (537), on adding solutions of disodium phosphate 
to one of zirconyl chloride. They obtained precipitates whose com- 
position was represented by the formula 5Zr0 2 .4P 2 5 .8H 2 0. Such 
uniformity in results is confirmatory evidence that these are not 
accidental or indefinite mixtures but are regularly formed when the 
conditions are even approximately duplicated. 

The experiments which have been detailed, therefore, show that 
when a solution of the zirconyl salt is added to an excess of a solu- 
tion of any of the phosphates the result is the formation of the 
pyrophosphate. When, however, these conditions are not observed 
the result is the formation of basic zirconyl phosphates which vary 
according to the previous history of the solution of the zirconyl salt 
or, in other words, the extent to which hydrolysis has proceeded. 
With the exception of such basic compounds or mixtures as have been 
mentioned above the pyrophosphate is the only zirconium phosphate 
known. The marked tendency to form this instead of the other phos- 
phates is noteworthy. 

As to compounds with other acids of phosphorus, Hauser and 
Herzfeld (299) have reported that on the addition of sodium sub- 
phosphate, Na 4 P 2 O 6 , in excess to a slightly warmed solution of zir- 
conyl nitrate in dilute hydrochloric acid a fine, crystalline precipitate 
practically insoluble in dilute acid was formed. The composition of 
this zirconium subphosphate was given as ZrP 2 6 .H 2 0, and this on 
ignition gives ZrP 2 7 . Thorium forms a similar compound, which 
would have to be borne in mind when this reaction is used for ana- 
lytical purposes. 

These authors also stated that when hypophosphorous acid was 
added to a solution of zirconyl nitrate in water there was formed an 
amorphous precipitate which slowly dissolved in an excess of the pre- 
cipitant. Any insoluble portion due to the presence of phosphates 
was filtered off. Electrolytic experiments showed the zirconium ions 
as complex, migrating with the negative stream. On the addition of 



92 ZIRCONIUM AND ITS COMPOUNDS 

alcohol a precipitate consisting of fine crystals was formed. These 
had strong refractive powers and exhibited a double polarization. 
The composition was that of the hypophosphite Zr(H 2 P0 2 ) 4 . When 
freshly precipitated the crystals contained one molecule of water 
which was easily separated. They showed a peculiar light sensibility. 
By direct sunlight they were rapidly colored deep violet. In diffuse 
light this took place only after the expiration of a number of weeks. 
No dissociation could be detected in these colored crystals under the 
microscope. 

Double Phosphates with Alkali Metals. Only those obtained with 
potassium and sodium phosphates are on record. With potassium the 
following compounds have been reported: Troost and Ouvrard (719) 
found that when zirconia or the phosphate or anhydrous zirconyl 
chloride were dissolved in fused potassium metaphosphate until no 
more was taken up and the cooled mass then leached with acidulated 
water to remove the excess of potassium metaphosphate there re- 
mained a double phosphate as a crystalline powder, apparently rhom- 
bohedric and belonging to the hexagonal system. These crystals acted 
strongly on polarized light and had a density of 3.18. They were 
not acted upon by acids nor aqua regia. The composition was 
K 2 0.4Zr0 2 .3P 2 5 . When fused, potassium pyrophosphate was used 
as the solvent and treated in the same way a crystalline powder of hex- 
agonal lamella? was left and this also acted on polarized light. These 
were soluble in H 2 S0 4 but insoluble in HC1 or HN0 3 . The density was 
3.08 and the composition K 2 O.Zr0 2 .P 2 5 . On adding potassium 
chloride to the above fusion to make it more fusible, the same salt 
was obtained and, in addition, another insoluble double phosphate 
forming small tetrahedral crystals, which was not further examined. 
Fusion with the orthophosphate K 3 P0 4 , gave no definite results, but 
when KC1 was added the same results were obtained as with the pyro- 
phosphate. When these double phosphates were heated to a very high 
temperature all was volatilized except the zirconia, which was left in a 
crystalline form. The density was 5.73 at 17. 

Sodium and Zirconium Phosphates. Knop (400) prepared a 
double phosphate of sodium and zirconium by fusing zirconia with 
sodium ammonium phosphate and keeping it at a white heat for two 
hours. After leaching the cooled mass with dilute hydrochloric acid 
and removing an amorphous portion there was left a crystalline meal 
consisting of colorless, transparent crystals in the form of rectangular 
parallelepipeds which acted on polarized light. These crystals have 



COMPOUNDS WITH ACIDS OF NITROGEN GROUP 93 

also been described by Wunder (825) as tetragonal combinations of 
prisms and basic pinacoids. Density determinations gave 3.12-3.14. 
They are insoluble in aqua regia. Analysis showed their composi- 
tion to be Na 2 0.4Zr0 2 .3P 2 5 , thus corresponding with the potassium 
compound. Troost and Ouvrard (719) using sodium metaphosphate 
as a flux with the addition of a small amount of sodium chloride, ob- 
tained rhombohedral crystals having a density of 3.10, whose com- 
position was also Na 2 0.4Zr0 2 .3P 2 5 . With sodium pyrophosphate 
as a flux small crystals whose form could not be well determined were 
obtained. The density was 2.88 and the composition corresponded 
to the formula 6Na 2 0.3Zr0 2 .4P 2 5 . These crystals acted slightly on 
polarized light, were optically bi-axial, and crystallized in hexagonal 
lamellae. When a large amount of salt was used in the fusion pris- 
matic crystals, which acted energetically upon polarized light with 
longitudinal extinction, were obtained. They were soluble in acids 
and had a density of 2.43. The analysis agreed with the formula 
4Na 2 O.Zr0 2 .2P 2 5 . 

Compounds with Arsenic Acid 

When disodium arsenate is added to a solution of Zr(S0 4 ) 2 a 
white powder is precipitated in a hydrated condition. Dried at 100 
there are two and a half molecules of water, Paykull (536) ; at 110, 
one molecule Kulka (417). Analysis showed the composition to be 
2Zr0 2 . As 2 5 . H 2 or 2.5H 2 O. When sodium arsenate was added to 
a dilute hydrochloric acid solution of ZrOF 2 a voluminous white pre- 
one molecule, Kulka (417). Analysis showed the composition to be 
3Zr0 2 .2As 2 5 .5H 2 (794). Berzelius (55) obtained an orange-yellow 
precipitate, which darkened on drying and was not decomposed by 
acids, by adding a solution of NaSH, saturated with As 2 S 3 , to a solu- 
tion of a zirconium salt. The supernatant liquid retained a yellow 
color. He called the precipitate zirconium sulpharsenite. He also 
stated that tri- and disodium sulpharsenates gave with zirconium salts 
citron-yellow precipitates which became orange-yellow on drying and 
were not decomposed by acids. 

Compounds with Antimonic Acids 

When a cold, neutral solution of potassium pyroantimonate is 
added to a solution of Zr(S0 4 ) 2 a curdy white precipitate is formed, 
insoluble in water but easily soluble in hydrochloric acid. The anal- 



94 ZIRCONIUM AND ITS COMPOUNDS 

ysis of the air-dried sample showed the composition to be 

Zr0 2 .Sb 2 5 .7.5H 2 0, or a hydrated pyroantimonate ZrSb 2 7 (417). 
i 

Compounds with Chromic Acid 

Weibull (794) reported that a precipitate was formed on adding a 
solution of chromic acid to one of zirconyl chloride, but no details 
were given as to the conditions observed in the experiment nor the 
composition of the product. Haber (276) stated that this precipitate 
was flocculent, orange-yellow in color, and difficultly soluble in dilute 
acid; also that the chromic acid could be gradually, though not com- 
pletely, leached out with water. Venable and Giles (748) made a 
more detailed examination of this reaction and the resulting product. 
The use of an alkali chromate as the precipitant is inadvisable on 
account of the persistent retention of the 'acid originally in combina- 
tion with the zirconyl, thus rendering the product impure. Zirconium 
hydroxide, prepared in the cold, was dissolved in a concentrated solu- 
tion of chromic acid. A portion of this solution allowed to evaporate 
over a dehydrating agent in partial vacuum yielded no crystals but 
gave a small amount of a reddish-yellow precipitate which was prob- 
ably a mixture of chromate and bichromate. When the solution was 
considerably diluted and boiled there was formed a yellow precipitate 
which was quite insoluble in water. This precipitate was granular 
or possibly very finely crystalline. The water of hydration was for 
the most part lost on heating at 100 and completely lost below 200. 
Analyses of several preparations corresponded to the formula 
Zr 3 5 . 2 3 on the dry basis, or, when the water present is taken into 
account, ZrO(OH) 2 .2ZrOCr0 4 .2H 2 0. 

Compounds with Tungstic Acid 

Kulka (417) added to a solution of zirconyl nitrate in the cold 
a solution of ammonium metatungstate, obtaining a gelatinous pre- 
cipitate. This precipitate, after boiling, was placed on a suction filter, 
washed with hot water, and then dried. The composition, deduced 
from the analysis, was 5Zr0 2 .9W0 3 .33H 2 0. By similar treatment 
of a precipitation made by means of sodium paratungstate a substance 
corresponding to the formula 5Zr0 2 .7W0 3 .21H 2 was obtained. The 
composition of these pecipitates was doubtless determined by the 
extent of the hydrolysis of the zirconyl salt used. These substances 
may be considered zirconium tungstic acids. 



COMPOUNDS WITH ACIDS OF NITROGEN GROUP 95 

Kulka also prepared a potassium salt by dissolving Zr(OH) 4 in a 
boiling solution of potassium paratungstate. On concentration the 
excess of potassium paratungstate crystallized out. There formed 
a crop of lengthened elliptical crystals, microscopic in size, which had 
the composition K 2 . Zr0 2 . 2W0 3 . 33H 2 0. No further crops differing 
in crystal form were obtained by him. 

Hallopeau (280) used a solution of potassium paratungstate 
(5K 2 0.12W0 3 .11H 2 0) in which he dissolved Zr(OH) 4 by prolonged 
boiling. The solution was alkaline. It was filtered clear and crys- 
tals separated on standing. These were redissolved in boiling water 
and re-crystallized. The crystals were microscopic and feebly active 
optically. Analysis showed them to be potassium zircono-decitung- 
state, 4K 2 . Zr0 2 . 10W0 3 . 15H 2 0. From the mother liquor separated 
a crop of very small prismatic crystals which acted with more energy 
upon polarized light with longitudinal extinction. These were potas- 
sium dizircono-decitungstate, 4K 2 0.2Zr0 2 .10W0 3 .20H 2 0. Twelve 
molecules of this water were lost on heating at 100. These zirconium 
compounds are less stable than the analogous ones of silicon. 

Likewise, by dissolving Zr(OH) 4 in a solution of ammonium para- 
tungstate and concentrating the solution over a dehydrating agent 
in partial vacuum to a syrupy consistency, there were obtained small, 
prismatic crystals which were strongly refractive and active to polar- 
ized light. They were easily dissolved in water and purified by re- 
crystallization. Their composition was that of ammonium-zircono- 
decitungstate, 3(NHJ 2 O.ZrO 2 .10W0 3 .14H 2 0. Most metallic chlo- 
rides, nitrates, etc., gave insoluble precipitates with these compounds. 

Berzelius (58) reported his experiments on the formation of zir- 
conium sulpho-tungstate. 

Compounds with Molybic Acids 

Since zirconium hydroxide is insoluble in ammonium molybdate 
solution, compounds can not be obtained by methods used for the 
tungstates. Kulka (417) prepared a molybdate by dropping a solu- 
tion of ammonium molybdate into a cold solution of Zr(SOJ 2 until 
a permanent precipitate was formed. The precipitate is gelatinous 
and can be washed free from (NHJ 2 S0 4 . It is insoluble in water 
but easily soluble in hot hydrochloric acid. The composition is 
Zr0 2 .2Mo0 3 .21H 2 zirconium molybdic acid. 

Salts of a somewhat similar acid have been prepared by Pechard 



96 ZIRCONIUM AND ITS COMPOUNDS 

(538) . The ammonium salt was formed by adding, in small portions, 
ammonium fluozirconate to a solution of ammonium molybdate. The 
solution acquires a deeper and deeper yellow color. When this change 
ceases the addition of an excess of hydrochloric acid causes the for- 
mation of ammonium-zirconium molybdate. This forms yellow octahe- 
dral crystals whose composition is 3(NH 4 ) 2 O.ZrO 2 .12Mo0 3 .10H 2 0, 
The potassium salt is prepared similarly. In this case the crystals 
are brown and may be several centimeters long, and effloresce on 
standing. The composition is 3K 2 O.Zr0 2 .12Mo0 3 .10H 2 0. These 
compounds are analogous to those of titanium and tin. 

Compound with Vanadic Acid 

A complex compound with vanadic acid has been prepared by 
Rogers and Smith (598). A solution of ammonium paratungstate 
was boiled for ten hours with an excess of zirconium hydroxide. Then 
ammonium phosphate was added and boiled two hours; and lastly, 
ammonium metavanadate, which had been reduced to the hydrate of 
the trioxide, was added and boiled two hours. Crystals separated 
from the concentrated solution in large black octahedra. They were 
very soluble in water. Nitric acid dropped on the crystals caused 
decomposition. The analysis showed the composition to be (NH 4 ) 2 
= 5.35; Zr0 2 =:0.63; V 2 3 = 14.28; P 2 5 =:2.49; W0 3 = 62.29; 
H = 14.96. This substance was named by the authors ammonium- 
zircono-vanadico-phospho-tungstate. Similar complexes have been 
prepared for silicon, titanium, tin, and thorium. 



Chapter VII 

Compounds with Acids of the Silicon Group 
Compounds with Titanic Acid 

According to Berzelius, a precipitate of zirconium titanate is 
formed on mixing solutions of zirconium and titanium chlorides and 
adding to this a solution of potassium sulphate. Details are lack- 
ing and artificially prepared titanates have not been further inves- 
tigated. A number of the zirconium minerals, however, carry appre- 
ciable quantities of titanium, also niobium and tantalum. In these 
it may be assumed that the oxides of the elements named form the 
acid constituents. Polymignite, for instance, contains 46.30 p.c. of 
Ti0 2 combined with 14.14 p.c. Zr0 2 , 12.2 p.c. Fe 2 3 , 2.7 p.c. Mn 2 3; 
4.2 p.c. CaO, the remainder consisting of the oxides of the rare earths 
with traces of other oxides. Mengite is chiefly Ti0 2 combined with 
Zr0 2 and Fe 2 3 . 

Compounds with Silicic Acid 

Zirconium Silicate. The natural silicate, known as the zircon or 
hyacinth, is the most abundant mode of occurrence of zirconium and 
also the most widely distributed. The crystal form is chiefly with 
the combination of faces [110], [111], often with a rhombohedral 
development and frequently thereby [311]. The faces [110] and 
[111] are usually well developed. An imperfect cleavage is shown 
along [110] and slightly also along [100] and [111]. They have a 
refractive action on light. They are to be classified as belonging to 
the tetragonal system of the bipyramidal class. The zircon is iso- 
morphous with thorite (ThSiOJ. 

The crystals are usually opaque and of a brown-red color. Others 
are transparent and variously colored, though some are colorless. The 
opaque crystals also have a range of colors, but these are rarer than 
the brown-red. They vary in size from microscopic to several inches 
in length. The hyacinth is transparent and of a deep red color. 

97 



98 ZIRCONIUM AND ITS COMPOUNDS 

These and the transparent crystals are classed with the precious 
stones. 

The zircon is found in igneous rock of various ages and also in 
the detritus from these. Though the zircon is very resistant to 
weathering agencies, a number of altered zircons are known. Among 
these may be mentioned alvite, anderbergite, auerbachite, beccarite, 
cyrtholit, oerstedtite, ostranite, and tachyaphaltite. 

The following analyses of the zircons (unaltered) may be cited 
as showing the average composition: 

Analyst Locality Zr0 2 SiOa Fe,0 8 

Klaproth Norway 65. 33. 1. 

Berzelius Expailly 67.16 33.48 

Damour North Carolina 65.30 33.21 

Chandler Ceylon 66.92 33.40 0.67 

Weatherell Reading 63.50 34.07 2.02 

Morehead North Carolina 62.83 33.98 

A qualitative analysis of zircon from Green River, N. C., by More- 
head (504) revealed the presence of Zr, Si, O, Fe, Na, K, Mg, Ca, 
Al, Pb, Sn, U, and Er. A more exhaustive analysis by Linnemann 
(449) gave nineteen elements as present, namely, Zr, Si, 0, Na, K, 
Li, Mg, Ca, Al, Fe, Mn, Cu, Pb, Sn, Zn, U, Er, Bi, and Co. Pereira- 
Forjaz (539) reported from his electrographic study of Portuguese 
zircons the presence of Zr, Si, 0, Ca, Al, Fe, Th, Ti, Mg, Sn, Bi, and 
Cu. Hannay (281) has reported traces of cerium and didymium. 
Thorium has been reported in a zircon from Schwalbenberg as present 
to the amount of 2.06 p.c. and yttrium as 3.47 p.c. (821). The iron 
content can be considerable, as much as 9 p.c. having been reported 
by Konig (406, 407). Some of these elements present doubtless may 
be regarded as impurities from infiltrations. The fairly regular pres- 
ence of the five group analogues, Si, Ti, Th, Sn, and Pb, is, however, 
noteworthy. Zirconium also shows many analogies to the aluminum 
and iron which are always present. The absorption spectrum given 
by many zircons is ascribed to the uranium and rare earths present 
(36). As uranium is said to be always present, the radio-activity 
observed and also the accompanying lead may be assigned to this 
element. Zircons may be freed from iron and, in some cases, opaque 
zircons may be rendered transparent by heating them in an atmos- 
phere of carbon tetradhloride, carbonyl chloride, or sulphur chloride. 
Baddeleyite, the native zirconia ore from Brazil, also contains 
several of the analogous elements of the fourth group. In connection 
with it is found another natural zirconium silicate which may contain 



COMPOUNDS WITH ACIDS OF THE SILICON GROUP 99 

as much as 75 p.c. of zirconia. This would appear to be a basic sili- 
cate. It differs from the ordinary zircon in its complete solubility in 
dilute hydrofluoric acid, which leaves the zircon unattacked. This is 
called zirkelite. 

Zircon is not acted upon by dilute or concentrated acids. Hydro- 
gen fluoride attacks it only at high temperatures. If mixed with 
carbon and heated to a high temperature it is acted upon by fluorine 
and chlorine. Its melting point has been lately determined (762) as 
2550. A mixture of Zr0 2 and Si0 2 in molecular proportions melts 
at the same temperature (762). Cussak (158) failed to melt it when 
using a Joly meldometer and drew the conclusion that the melting 
point was 1760 or higher. It is slowly taken up in a fusion with 
borax, also in microcosmic salt (340). The fusion with potassium 
or sodium hydroxide is also difficult and imperfect. The addition, 
however, of moderate amounts of sodium fluoride brings about a rapid 
and complete fusion. 

The density of the zircon ranges from 4.0 to 4.7; the hardness 
from 7 to 8 therefore approaching that of the diamond. The formula 
is ordinarily written ZrSi0 4 . Vegard (727, 728, 729, 730), from his 
study of the crystal lattice structure, reached the conclusion that the 
formula should be written Zr0 2 .Si0 2 , since the zirconium and silicon 
atoms were found to be similarly placed in regard to the oxygen 
atoms. 

Luminescence of Zircons. It has long been known that zircons 
from certain localities, as Norway and Expailly, phosphoresce when 
heated to the temperature of low redness. Some of the zircons under 
this treatment become colorless and transparent; also, in most cases 
the density is permanently increased. A number of investigations 
have been made as to the cause and possible interrelation of these 
phenomena. Damour (161) has shown that there is slight and 
often inappreciable loss in weight on heating. Also, he has pointed 
out that the index of refraction is changed as well as the density, and 
that the increased density remains unchanged even when the heating 
is pushed to fusion, except in one or two of the cases examined. He 
suggested that it might be a matter of allotropism, the action of heat 
bringing about a change into the second allotropic modification. 
Fizeau (220) has shown that heat causes a lasting expansion of form. 
This would operate against an increase of density on heating. Ex- 
periments by Stevanovic (681), however, show that zircons having a 
density under 4.7 may have their density raised to that figure. The 



100 ZIRCONIUM AND ITS COMPOUNDS 

range of density of the native zircons is from 4.0 to 4.7. Where the 
zircon has this maximum density already it is unchanged on heating. 
The heating of a zircon then causes a slight loss of weight, which 
may be due to driving off some of the volatile constituents, a change 
of form, an increase in density, and a temporary phosphorescence. If 
the heating is for a brief period only, the phosphorescence may be 
re-induced by a repetition of the heating. After a few such re-heat- 
ings the. zircon loses the power of phosphorescing on the application of 
heat. In some of the theories advanced to explain this luminescence 
it has been assumed to bear some relation to the color of the zircon, 
which may also be lost on heating. According to Henneberg (316) 
the luminescence appears at a temperature below that at which the 
color is lost or changed. The loss of weight ranges from practically 
zero to 0.45 p.c. of the weight and the change of density from 1,0 to 
2.5 p.c. A brown-red color is lost at a temperature of about 300. 
Spezia (671) drew the conclusion from his experiments that this loss 
was due to the reduction of the ferric compounds present and main- 
tained that heating in a stream of oxygen restored the color. The 
experiments of Hermann (329) were more detailed and exhaustive 
and he agreed with Spezia that the color is largely due to iron in 
different stages of oxidation and, in the case of a green color, to an 
admixture of chromic oxide. Doelter (193) concluded from his in- 
vestigation that Spezia was wrong in assuming that iron confers the 
color and thought it to be due to some unknown substance of a col- 
loidal nature. With regard to density, he found the green zircon 
to have the lowest, and colorless zircon to have the highest. Green 
and yellow zircons, he believed, had a different coloring matter from 
the brown and red. Stevanovic (681) stated that the biaxial green 
zircon with a density of 4.3 changed on heating into the uniaxial, nor- 
mal zircon with a density of 4.7. These phenomena attracted the 
attention of several earlier investigators and led to experiments on 
their part, but the varying accounts as to the properties and behavior 
of zircons may in part be explained by the somewhat wide variations 
of the minerals coming from different localities, the faulty methods 
of the investigators, and the neglect on their part to exclude the in- 
filtrations of foreign matter which necessarily vitiate their results. 
Due precautions were taken by Doelter and other recent workers to 
remove, as far as possible, such matter as did not form a component 
part of the crystals. The cathode luminescence of the zircon was 
examined by Crookes (154) and Pochettino (558). 



COMPOUNDS WITH ACIDS OF THE SILICON GROUP. -Jfll 



Further light has been thrown on these changes of color in zircons 
by a study of their radio-activity and the action of radium emana- 
tions upon them. The radio-activity of zircons is markedly greater 
than that of any other hard mineral occurring in igneous rock. Fur- 
ther, zircons contain hundreds of times more helium than the average 
rock with which they are associated and Strutt (690) has made use 
of this fact as a means of determining the geologic age of the sur- 
rounding rock. This radio-activity was in excess of the uranium or 
thorium contents and indicated the presence of an accumulation of 
radium. The uranium-lead ratio has been determined by Holmes 
(351), the percentage of uranium found being 0.0019 and of lead 
0.000085. Zircons show also a greater radio-activity than any other 
mineral associated with monazite. Zircon crystals in plutonic rocks 
are opaque. Those in basalt and lavas are transparent and show 
signs of incipient fusion (690). The transparent crystals are ther- 
moluminescent, giving out a phosphorescent glow and losing color 
when moderately heated (200). The glow is not repeated if once 
heated until it disappears. Partial heatings bring out the glow until 
the property is lost. It can be restored, and also the color, by expo- 
sure for some weeks or months to the emanations from radium salts. 
Opaque crystals are not thermoluminescent nor made so by exposure 
to radium. Nor are they decolorized by moderate heating. If kept 
in melted basalt for twenty-four hours they become white, though 
not transparent, and then on exposure to radium emanations they 
become reddish-brown like the hyacinth and thermoluminescent. This 
treatment, however, does not make them transparent. It has been 
stated by Demarcay (174) that zircons lose their color when heated 
in a stream of carbon tetrachloride. Splinters of opaque zircons be- 
come transparent when heated in such an atmosphere or in one of 
carbonyl chloride, these reagents removing the iron, aluminum, and 
probably some other minor constituents. 

To the radio-activity of zircons has been assigned (379) the pro- 
duction of the pleiochroitic halos observed in the enclosing biotite, 
iolite, etc. The color of zircons in monazite resembles that given to 
the glass containers by radium salts. This color penetrates the crys- 
tals. The theory of Doelter (194) that the colors of zircons may be 
due to some element in a colloidal state is in harmony with many 
of the known facts and receives support from the behavior toward 
radium emanations (490) . The separation of the finely-divided, col- 
loidal metal through the action of the rays is a possibility and it is 



402 - ;;-.,< ZIRCONIUM AND ITS COMPOUNDS 



well known that the colorings given by a metal in this state may be 
greatly varied. It must be noted that not all zircons are affected by 
radium. Brauns (100) found that originally colorless specimens ex- 
amined by him could not be colored. Grengg (260) believed that the 
finely-divided iron oxide surrounding zircon crystals in porphyries, 
which resembles the halos often surrounding zircon enclosed in biotite, 
was due to the decomposition of iron-bearing solutions circulating 
through pore spaces of the ground mass by emanations from zircon 
crystals. 

As an accompaniment of radio-activity helium is found in zir- 
cons, euxenite (556), malacone (391), baddeleyite (9), and other zir- 
conium minerals. Only 20 p.c. of the helium in malacone (whose 
radio-activity is very slight) could be attributed to the uranium pres- 
ent. The remaining 80 p.c. was due to something else, possibly 
radium, according to Kitchin and Winterson (391). On decomposing 
the mineral and treating it to separate the zirconia they found that 
the activity remained with the zirconia and insoluble material. Gum- 
ming (155) varied the treatment and found the soluble portion active. 
According 'to his treatment, this should have contained the radium. 
Kitchin and others have found that the helium in malacone was 
accompanied by argon, and Antropoff (9) detected argon in a zir- 
conium mineral from Brazil. These anomalous observations have not 
been refuted nor any explanation offered. The same may be said of 
the observation by Ramsay and Usher (581) that a solution of zir- 
conyl nitrate yielded carbon dioxide and carbon monoxide under the 
influence of radium emanations, as did solutions of the analogues 
- Si, Ti, Th, and Pb. 

Artificial Zircons. Deville and Caron (183) by passing at a high 
temperature silicon fluoride over zirconia or, reversing this, zirconium 
fluoride over quartz, obtained small octahedral crystals, transparent, 
brilliant, and having approximately the hardness and density of zir- 
cons. Hautefeuille and Margottet (306) by fusing a mixture of zir- 
conia and silica in glacial phosphoric acid prepared a zirconium sili- 
cate. Hautefeuille and Perrey (309) on heating for a month two parts 
of zirconia and one part of silica with lithium dimolybdate to a tem- 
perature of 700-1000 obtained ditetragonal, bipyramidal crystals 
having a density of 4.6. The crystal combination was [110], [HI]. 
Chrustschoff (140) heated a mixture of the two hydroxides Si(OH) 4 
and Zr(OH) 4 in a closed platinum crucible which was enclosed in a 
steel block for two hours at a red heat, thus securing a high pressure 



COMPOUNDS WITH ACIDS OF THE SILICON GROUP 103 

in addition to the heat. The crystals were well-formed and up to 
0.18 mm. in length. The density was 4.45. 

Natural Double Silicates. Ordinary zircon is probably a mixture 
of zirconium silicate with small amounts of various double silicates. 
Certain other minerals are regarded as distinctively double silicates. 

Catapleiite (H 2 (Na 2 .Ca)ZrSi 3 O 11 ). Hardness 6; Sp. Gr. 2.8; 
monoclinic prismatic; cleavage perfect. On heating the crystals be- 
come uniaxial and go over into the hexagonal. 

Elpidite (Na 2 Si 2 O 5 .Zr(Si 2 5 ) 2 ). Sp. Gr. 2.5-2.6; rhombic pris- 
matic. 

Eudialyte (Na 13 (CaFe) 6 (SiZr) 20 52 Cl). Groth regards the chlo- 
rine as due to some small admixture, as sodalite, and assigns the for- 
mula Na 2 0.2(CaFe)0.6(SiZr)0 2 . 

Lovenite (Ca.Fe.Mn.Na.ZrOF. (Si0 3 ) 2 ). Monoclinic; hardness 
6; Sp. Gr. 3.5. 

Wohlerite (Na 7 Ca 10 Fe 3 Zr 3 Si 10 42 F 3 ) . This may also be men- 
tioned. 

Artificial Silicates. A. Potassium zirconium silicate (K 2 O.ZrO 2 .Si0 2 ) . 
This is formed by melting together at a bright red heat one part of 
zircon . and four parts of potassium carbonate for fifteen minutes. 
If the heating is prolonged potassium silicate and crystalline zirconia 
are the products according to Ouvrard (531). This double silicate 
crystallizes in rhombic prisms (224). These are acted upon by hydro- 
fluoric acid and ammonium fluoride (531). 

B. (K 2 O.Zr0 2 .2Si0 2 ). One part of pulverized zircon with two 
to four parts of caustic potash are heated in a silver crucible. The 
mass is leached with cold water, leaving the double silicate as a 
finely-divided powder (138, 46). The complete removal of the silica 
by prolonged heating with potassium carbonate was confirmed by 
Knop (400) . When the fused mass was leached with water potassium 
silicate was dissolved out and potassium zirconate was left. Melliss 
(479) by a similar fusion obtained a microscopic, crystalline residue 
which on analysis proved to have the composition K 2 . Zr0 2 . 2Si0 2 . 
The density was 2.79. 

Sodium Zirconium Silicate (Na 2 0.8Zr0 2 .Si0 2 .llH 2 0). This 
was prepared by Melliss (479) by the method used for the potassium 
compound, removing all soluble matter by leaching with water. The 
crystals were microscopically small, transparent, hexagonal prisms 
and had a density of 3.53. The water of hydration was lost at low 
red heat without indication of further decomposition. Sulphuric acid 



104 ZIRCONIUM AND ITS COMPOUNDS 

decomposed the crystals. Another sodium zirconium silicate with the 
composition Na 2 . Zr0 2 . Si0 2 was obtained by Gibbs (244) by fusing 
one part of zircon with four parts of sodium carbonate and leaching 
the residue by repeated boiling with a concentrated solution of sodium 
carbonate. The granular white powder which was left was washed 
with lukewarm water without decomposition. Bourgeois (94) added 
silica to powdered zircon and kept the mixture at red heat for twenty- 
four hours with a small amount of melted sodium carbonate. He 
found that a considerable excess of sodium carbonate decomposed the 
salt. He determined the crystalline form as rhombic prisms, 0.5 mm. 
broad and several mm. long. The facial combination was of [110] 
and [010] with angles of almost exactly 60 without end planes. 
The extinction was parallel and there was double refraction. The 
powder obtained by Gibbs (244) was decomposed by hot water and 
hydrochloric acid, and formed a jelly of silicic acid. The crystals 
obtained by Bourgeois were soluble in concentrated acids. There is 
doubt as to the formation of double silicates by these methods. Ac- 
cording to Scheerer (638) and others, only the zirconates are formed 
in this way. 

Calcium Zirconium Silicate. Berthier (46) made various trials 
at fusing zircon, quartz, and marble in carbon crucibles. The propor- 
tions were varied and some of the products were glassy, some enamel- 
like, and some dull and stonelike. The extent of fusion differed, as 
did also that of the homogeneity of the product. No definite com- 
pounds were reported. As has been stated, calcium is found in many 
natural zircons and these may contain small amounts of calcium 
zirconium silicate. 

Berthier (46) also reported the results of his experiments in fusing 
zircon and litharge together. Two experiments were carried out on 
a small scale. The first yielded a translucent yellow mass, which on 
analysis gave Si, 0.097; Zr, 0.19; and PbO, 0.71. The second was semi- 
translucent and not homogeneous, showing partly olive and partly 
green coloration. The analysis gave Si, 0.15; Zr, 0.30; and PbO, 0.55. 
There is no proof of a definite lead zirconium silicate but some evi- 
dence that in some form the lead enters into the combination. 



Chapter VIII 
Zirconic Acid and the Zirconates 

It would seem necessary to repeat here some facts already noted 
under the zirconium hydroxides. Normal zirconium hydroxide is 
readily dehydrated with the loss of one molecule of water: 
Zr(OH) 4 = ZrO(OH) 2 + H 2 0. The change takes place in the 
presence of water on standing and is accelerated by heating. The 
resulting zirconyl hydroxide, ZrO(OH) 2 , is amphoteric, reacting with 
acids to form salts, as ZrO(OH) 2 + 2HC1 = ZrOCL, + 2H 2 0. It 
reacts with bases to form salts of an acid, H 2 Zr0 3 , or zirconic acid. 
Analogous acids are H 2 Si0 3 , H 2 Ti0 3 , and H 2 Sn0 3 . Whether a meta- 
zirconic acid may be formed also has not been definitely settled. 
Van Bemmelen (34) has adduced arguments in favor of the existence 
of such an acid. Complex compounds, which have been called poly- 
zirconates and which may correspond to the polysilicates, are known. 
The hydroxide, ZrO(OH) 2 or Zr0 2 .H 2 0, has been prepared by Ruer 
(619) and others by carefully drying the hydroxide (precipitated from 
either cold or hot solutions) at 100, and by Van Bemmelen (34) by 
drying at 140. The last molecule of water is practically removed at 
300, though it is partly lost at a somewhat lower temperature. The 
hydroxide, if dried below 200, may be rehydrated, but if heated above 
that temperature rehydration is difficult and imperfect. If the tem- 
perature is raised rapidly to 300 while as much as one-third or more 
of this last molecule of water is still present, sudden dissociation 
takes place with the evolution of heat accompanied by light, and 
hence the loss of potential energy. The hydroxide ZrO(OH) 2 forms 
a hydrogel which may be obtained in the colloidal state. Observers 
have reported the radical ZrO as migrating with either the positive or 
negative stream. 

Zirconates. Zirconic acid combines with strong bases to form com- 
pounds which are insoluble in water and are decomposed by acids. 
The slight solubility of zirconyl hydroxide in solutions of strong bases, 
as the caustic alkalies, practically limits the preparation of these 
compounds to fusion methods. The fact that when zirconium hydrox- 

105 



106 ZIRCONIUM AND ITS COMPOUNDS 

ide is precipitated by an alkaline hydroxide some of the latter is 
persistently retained has been looked upon as an indication that a 
compound has been formed. The alkali, however, can be removed 
by thorough washing and is doubtless merely adsorbed by the col- 
loidal hydroxide. There is similar adsorption of acids, salts, etc. 
Some of the products of the fusion methods have been obtained in a 
crystalline form, others as powders only. The difficulty of deciding 
when a fusion reaction is complete leaves it uncertain at times as to 
whether unattacked zirconia is present, and no entirely reliable method 
for its separation has been used. The usual method is to wash free 
from the excess of base and then decompose and dissolve the zir- 
conate with dilute acid. Discordant results, which seem to be due 
to the temperature or length of fusion, have been reported. It is 
noteworthy that experiments with the alkali bases show a wide varia- 
tion and a tendency to form polyzirconates, while those with the 
alkaline earths are quite uniform, giving normal salts of zirconic 
acid. 

Sodium Zirconates. When powdered zircon is heated for a con- 
siderable time at a high temperature with sodium carbonate and the 
resulting fused mass, after cooling, is thoroughly leached with water 
there is left, according to Knop (400), a crystalline sodium zirconate 
which is decomposed by hydrochloric acid. Ouvrard (531) stated 
that on using the same method he obtained only crystallized zirconia. 
If the temperature used by Ouvrard were high enough to volatilize the 
alkali this discrepancy might be explained, or the insolubility of the 
residue in water may have been considered sufficient proof that only 
zirconia was present. Earlier observations led to the belief that the 
zirconates were soluble and this error was repeated in books of ref- 
erence. 

Hjortdahl (342) attempted to determine the formation of sodium 
zirconates and their composition by heating together zirconia and 
sodium carbonate and measuring the carbon dioxide given off. Thus, 
when these two in approximately molecular proportions were kept at 
a dark red heat for nine hours all of the carbon dioxide was liberated 
and there was left a crystalline mass which was hygroscopic and on 
treatment with water yielded sodium hydroxide and an amorphous 
mass. From the carbon dioxide lost he concluded that a compound, 
Na 2 O.Zr0 2 , had been formed, although he also heated sodium car- 
bonate by itself and measured the carbon dioxide lost. The fusion 
was likewise repeated with powdered zircon and the same material 



ZIRCON 1C ACID AND ZIRCONATES 107 

by Scheerer (638) and Hermann (319), each concluding that the 
material left after leaching with water was sodium zirconate. 

Venable and Clarke (747) found that when zirconia was added 
to a clear melt of sodium carbonate it sank to the bottom and re- 
mained apparently unattacked for hours. In a number of experi- 
ments it was found that 90 p.c. and over of the zirconia was unaltered. 
After thorough leaching with water the mass was treated with dilute 
hydrochloric acid and the proportions of zirconia and soda in the 
solution determined. In two experiments the ratio was 2Na 2 . 3Zr0 2 . 
In a third, where the heating was twice as long, the ratio was approxi- 
mately 3Na 2 0.2Zr0 2 . When sodium hydroxide was substituted for 
the carbonate a much larger amount of the zirconia entered into the 
reaction (40-60 p.c.). The ratio of Na 2 to Zr0 2 in the hydrochloric 
acid solution was only from 6.7 to 7.8 Na 2 to 93.3-92.2 Zr0 2 . 

A so-called sodium perzirconate has been prepared by Pissarjewski 
(555) by mixing two grams of freshly prepared hydrated zirconium 
trioxide with 200 c.c. of hydrogen peroxide solution (2 p.c.) and 
16 c.c. of sodium hydroxide solution (19.5 p.c.). On the addition of 
double the volume of alcohol an emulsion was first formed and then 
a flocculent precipitate. This was separated, dissolved in water at 
0, more hydrogen peroxide added with a few c.c. of sodium hydroxide, 
and then about three-fourths the volume of alcohol. The precipitate 
was washed with alcohol and ether and became a loose powder which 
was partially dried over dehydrating agents, washed again with 
alcohol and ether, and dried between filter paper and analyzed. This 
substance liberated hydrogen peroxide when treated with dilute sul- 
phuric acid, and ozone and oxygen with concentrated sulphuric acid. 
The composition calculated from the analysis was Na 4 Zr 2 11 .9H 2 0. 
It is difficult to classify this substance and the similarly prepared 
E^ZrAi-BH.O. 

Potassium Zirconates. It is not practicable to prepare potassium 
zirconate by fusing zirconia in potassium carbonate because of its 
very slight solubility in that substance. Venable and Clarke (747) 
found that only 0.5 p.c. was dissolved after ten hours' heating. When 
potassium hydroxide was used from 45-75 p.c. was taken up, forming 
a compound which was insoluble in water but soluble in dilute acid. 
The composition varied when simply leached with water and the 
zirconate then taken up with dilute hydrochloric acid, indicating, 
perhaps, a partial decomposition of the zirconate. When dilute acetic 
acid was substituted for the leach water a substance was left which 



108 ZIRCONIUM AND ITS COMPOUNDS 

had the approximate composition K 2 . 3Zr0 2 . This agreed with some 
of the results of Hjortdahl (342). It may be called a polyzirconate. 

Potassium perzirconate (K 4 Zr 2 1 .9H 2 0) has been prepared by 
Pissarjewski (555) and shows the same properties as the sodium com- 
pound. 

Lithium Zirconate. When lithium chloride is fused for some 
hours with zirconia or powdered zircon and the mass extracted with 
water, prismatic crystals with longitudinal extinction are left. These 
are soluble in acids. The composition is Li 2 O.Zr0 2 or Li 2 Zr0 3 (531). 
The mass must be kept at a high temperature, as ordinary fusion 
shows little action (747). Fusion with lithium carbonate gives a 
strong evolution of carbon dioxide and zirconia crystallizes out of 
the melt. 

Lithium Perzirconate. This substance was prepared (531) by 
fusing zirconia in lithium hydroxide and leaching the melt with dilute 
acetic acid. It had the composition Li 2 0.2ZrO 2 or Li 2 Zr 2 5 . 

Magnesium Zirconate. When a mixture of silica and zirconia is 
fused with magnesium chloride in a platinum crucible whose bottom 
is covered with ammonium chloride and the melt is raised quickly to 
a white heat and kept at that temperature for an hour (some of the 
magnesium chloride volatilizing and hence necessitating the use of 
an excess), a mixture of octahedral and prismatic crystals which can 
not be well separated is obtained. The prismatic crystals are re- 
ported as having the composition MgO.Zr0 2 (342). By heating a 
mixture of four parts of magnesium oxide and one part of zirconia 
and leaching the product with dilute acetic acid a crystalline salt with 
the same composition, MgO.Zr0 2 or MgZr0 3 (747), is prepared. 

Calcium Zirconate. Hjortdahl (343) reported an acid calcium 
zirconate which he prepared by heating powdered zircon or a mixture 
of silica and zirconia with an excess of calcium chloride for five or six 
hours at a bright red heat and leaching the product with dilute hydro- 
chloric acid. It was described as a brilliant crystalline powder. The 
normal zirconate was prepared by Ouvrard (532) by heating zirconia 
in melted calcium chloride for 20-30 hours. The product was leached 
with water and a crystalline substance having the composition 
CaO.Zr0 2 was left. According to Venable and Clarke (747) this 
reaction takes place only after calcium oxide has been formed. They 
heated zirconia for many hours with calcium oxide and leached the 
product with dilute acetic acid. The crystals obtained (532) had a 
strong action upon polarized light and were apparently isomorphous 



ZIRCONIC ACID AND ZIRCONATES 109 

with calcium stannate and calcium titanate. The compound is the 
normal calcium zirconate, CaZr0 3 . 

Strontium Zirconate. Ouvrard (532) prepared this compound by 
fusing zirconia with strontium chloride. The reaction was brought 
about with greater difficulty than in the case of calcium zirconate. 
The crystals are similar to those of calcium zirconate. Venable and 
Clarke (747) fused zirconia with strontium oxide and leached the 
mass with dilute acetic acid. Both found the composition to be 
SrO.Zr0 2 or SrZr0 3 . 

Barium Zirconate. Ouvrard (532) obtained opaque crystals by 
fusing zirconia with barium chloride (difficult). Venable and Clarke 
(747) found that there was vigorous reaction when zirconia was fused 
with barium hydroxide. The product was leached with dilute acetic 
acid. It was crystalline. The composition was BaO.ZrO 2 or BaZrO 3 . 



Chapter IX 

Organic Compounds 
Compounds with Organic Acids 

Carbonic Acid. It has been stated by early investigators that 
moist, gelatinous zirconyl hydroxide readily absorbs carbon dioxide 
from the air (43, 537). If the hydroxide is heated to 100-150 in a 
stream of carbon dioxide for twenty-five to thirty hours the amount 
absorbed may exceed 16 p.c.; if suspended in water, as much as 7 p.c. 
may be taken up. This absorbed carbon dioxide is given off by the 
dried substance in a current of air, as much as 30 p.c. being lost in 
this way and the remainder on heating (743). When solutions of 
alkali carbonates are added to solutions of zirconyl salts, white floc- 
culent precipitates soluble in an excess of the precipitant are formed. 
Boiling water poured on these precipitates causes the evolution of 
carbon dioxide with foaming. On being washed with cold water and 
dried over sulphuric acid the composition of such a precipitate in one 
analysis made was 3Zr0 2 . Co 2 . 6H 2 (319). The solubility in an 
excess of alkali carbonate has been regarded as proof of the formation 
of double carbonates. It is possible that basic zirconyl carbonates 
are formed by some of these methods, but there is no evidence of the 
preparation of a normal zirconyl carbonate. Whatever compound is 
formed is very unstable, as is to be expected with so weak an acid. 

Formic Acid. The addition of formic acid or an alkali formate 
to a solution of a zirconyl salt gives a precipitate which is soluble 
in an excess of the formate. An analysis of such a precipitate yielded 
Zr0 2 76.35 and HC0 2 H 19.0 (466) . When zirconium tetrachloride is 
dissolved in anhydrous formic acid all of the chlorine is liberated as 
hydrogen chloride and a crystalline crust, which is zirconium formate 
(Zr(HC0 2 ) 4 ), is obtained (611). 

Acetic Acid. Only insignificant amounts of zirconyl hydroxide 
are dissolved by either hot or cold acetic acid, even when glacial acetic 
acid is used (466, 743) . The evaporation of such a solution leaves an 
amorphous powder which is soluble in water or alcohol (395, 722). 
This deposit has 'been described by Berzelius as being very hygro- 

110 



ORGANIC COMPOUNDS 111 

scopic, and also as being gummy, Mandl (446). It is manifest that 
the method is inapplicable for the preparation of a definite compound. 
When sodium acetate is added to a neutralized solution of zirconyl 
chloride and the whole heated the zirconium is completely precipitated 
as a voluminous, flocculent basic acetate. This is soluble in warmed 
glacial acetic acid and the evaporation of this solution leaves a brittle, 
gumlike mass (276) . The re-solution of such a basic acetate in acetic 
acid does not yield a neutral acetate. The addition of acetic acid to 
a solution of a zirconyl salt causes an immediate precipitate which is 
redissolved by more acid (446). 

Zirconium Acetate (Zr(C 2 H 3 2 ) 4 ). Rosenheim and Hertzmann 
(611) prepared this salt by dissolving zirconium tetrachloride in boil- 
ing anhydrous acetic acid. After driving off the hydrochloric acid by 
heating the salt separated on cooling as microscopic prisms, easily 
soluble in water of alcohol but insoluble in ether. It is not very 
stable in air, losing acetic acid. The aqueous solution is quickly 
hydrolyzed. 

The acetate is more quickly and completely hydrolyzed at a lower 
temperature than the salts of mineral acids. The hydrolysis was 
measured by the relative conductivity method and calculated in recip- 
rocal ohms. The temperature at which the measurements were made 
was 25 (611). 

Time Elapsed 

5Min. 25Min. 45 Min. 18 Hrs. 23 Hrs. 41 Hrs. 
284.2 X 10- 6 289. X 10 6 291. X 1Q- 6 310. X 10' 6 310. X 10' 6 310. X 10' 6 
Specific conductivity of the equivalent of acetic acid at 25 = 
289. X 10- 6 . 

The acetate lends itself especially to preparing the colloidal hy- 
droxide for mordanting and similar purposes. 

Zirconyl Acetate (ZrO(C 2 H 3 O 2 ) 2 ). This is formed when the nor- 
mal acetate is allowed to stand for a number of days over sulphuric 
acid. The normal zirconyl acetate is stable in dry air and is soluble 
in water or alcohol. In moist air it is hydrolyzed, giving insoluble 
basic products. 

The chloracetic acids, butyric acid, propionic acid, etc., show a 
behavior analogous to that of acetic acid. 

Citric Acid. Harris (286) reported the formation of a double 
citrate of zirconium and ammonium by the addition of ammonium 
citrate to a solution of zirconyl chloride. There was formed a white, 



112 ZIRCONIUM AND ITS COMPOUNDS 

curdy precipitate which was washed and dried at 120. It was 
very deliquescent. The analysis corresponded to the formula 
Zr 2 .C 6 H 5 7 .(NH 4 ) 3 . 

Oxalic Acid. Oxalic acid is the best solvent for zirconyl hydroxide 
among the organic acids, approaching the mineral acids in this respect 
(681). Solutions of zirconyl salts are precipitated by oxalic acid or 
ammonium oxalate, giving a gelatinous or flocculent precipitate which 
is nearly insoluble in water or dilute oxalic acid (202) . Zirconyl sul- 
phate presents some anomalies in this regard. This has been investi- 
gated by Ruer (617) and explained on the hypothesis of the forma- 
tion of a zirconium-sulphuric acid, a supposition not accepted by later 
investigators. The precipitate formed with oxalic acid carries prac- 
tically all of the zirconium. It was found by Venable and Basker- 
ville (741) to be basic and to show a variable composition. It was 
nearly insoluble in dilute acids. Paykull (536) reported the prepara- 
tion of an amorphous zirconyl oxalate, ZrOC 2 4 , and one with two 
molecules of water, ZrOC 2 4 .2H 2 0. Rosenheim and Frank (610), 
on adding a solution of oxalic acid to one of a zirconyl salt, obtained 
a gelatinous precipitate which settled poorly and was filtered with 
difficulty. The addition of a solution of NaC 2 H 3 2 caused the pre- 
cipitate to settle readily, and it could be washed and filtered without 
difficulty. The air-dried precipitate was insoluble in cold water but 
was hydrolyzed by hot water. The composition was ZrOC 2 4 .4H 2 0. 
When a boiling solution of oxalic acid was saturated with zirconyl 
hydroxide and the solution concentrated over H 2 SO 4 mixtures of large, 
clear, prismatic crystals of the oxalate and needlelike crystals of 
oxalic acid were obtained. These were separated mechanically 
and the oxalate analyzed. The formula given (610), namely, 
ZrOH(C 2 4 ) 3 .7H 2 0, presents many difficulties. The compound is 
probably identical with that obtained by Venable and Baskerville 
(742) by analysis of the one formed when the precipitated oxalate is 
dissolved in a solution of oxalic acid to which some hydrochloric acid 
has been added. The analyses made by these authors gave the 
formula Zr(C 2 4 ) 2 .H 2 C 2 4 .7 (or 8) H 2 0. The salt forms fine, pris- 
matic crystals. 

An ammonium zirconium oxalate (2(NH 4 ) 2 C 2 4 .Zr(C 2 4 ) 2 ) has 
been reported by several investigators: Water- free (697), 4 molecules 
H 2 (536) , 6 molecules H 2 (440) . It can be prepared by dissolving 
zirconyl hydroxide in an excess of oxalic acid and nearly neutralizing 
with ammonia. Crystals form from the solution (742). These crys- 



ORGANIC COMPOUNDS 113 

tals also form when ammonium oxalate is added to the oxalic acid 
solution of the hydroxide which should contain free acid (537) . These 
crystals have been described as octahedra and as small monoclinic 
crystals. They dissolve in either cold or hot water without dissocia- 
tion (507). A simpler method of preparation is to saturate a solu- 
tion of an acid alkali oxalate with zirconium hydroxide. The formula 
has also been written Zr(C 2 O 4 R) .5H 2 O where R represents the am- 
monium radical or an alkali metal (576) . 

Tartaric Acid. Zirconyl hydroxide dissolves in tartaric acid in a 
proportion of less than 1 : 1000. It is ten times more soluble in an 
ammoniacal solution of ammonium tartrate. The composition of the 
precipitate formed by adding a solution of tartaric acid to solutions 
of zirconyl salts varies under differing conditions of precipitation 
(794). The results obtained by Hornberger (356) do not accord with 
more recent investigations. Rosenheim and Frank (610) found that 
on adding tartaric acid to a solution of zirconyl chloride the precipi- 
tate settled well and was easily filtered. When air-dried it formed an 
amorphous powder, insoluble in water, easily soluble in mineral acids 
and caustic alkalies. It could be reprecipitated from the latter with- 
out alteration by the addition of acid. Various preparations under 
differing conditions yielded on analysis results corresponding to the 
formula Zr 3 (OH) 8 .C 4 H 4 6 .6H 2 (611). The analyses reported fail 
to agree closely. By adding two atoms of hydrogen the formula may 
be rewritten 2ZrO(OH) 2 .ZrOC 4 H 4 6 .7H 2 O. This is probably only 
one of several basic tartrates which may be formed under more widely 
differing conditions. The solubility in caustic alkali indicates the 
existence of double tartrates. Rimbach and Schneider (593) observed 
that the addition of solutions of zirconyl salts to alkali tartrate solu- 
tions increased the action on polarized light. The above-mentioned 
basic tartrate, when dissolved in just the necessary amount of caustic 
alkali and the solution evaporated to a syrupy consistency, gave small, 
needlelike crystals which were very soluble in water. Analysis gave 
the composition as K 2 C 4 H 4 6 .ZrOC 4 H 4 G .3H 2 0, which was reported 
(609) as ZrO(C 4 H 4 6 K) 2 .3H 2 O. The same compound was prepared 
by mixing solutions so as to give the ratio two molecules of tartaric 
acid, one molecule of zirconyl nitrate, and four molecules of potassium 
hydroxide. Potassium nitrate first crystallized out and then potas- 
sium zirconium tartrate. The analogous sodium salt was not ob- 
tained. Solutions of zirconium tartrate in ammonium hydroxide gave 
products which were unstable, losing ammonia on standing. Rosenr 



114 ZIRCONIUM AND ITS COMPOUNDS 

heim and Frank (610) looked upon the fact that many of these com- 
pounds with organic acids, when prepared under varying conditions, 
show a constant composition as evidence that they are definite com- 
pounds and not adsorption compounds as maintained by Miiller (512). 

Benzole Acid. A compound of the normal zirconium benzoate 
with ZrCl 2 has been prepared (611) by the action of an ethereal solu- 
tion of benzoic acid at the boiling temperature upon zirconium tar- 
trate, the boiling being continued so long as hydrogen chloride was 
liberated. The reaction proceeds according to the equation 
ZrCl, + 2C 6 H 5 . C0 2 H = ZrCl 2 (C 6 H 5 . C0 2 ) 2 + 2HCL The radical 
ZrCl 2 functions apparently as the radical ZrO. Stronger monocar- 
boxylic acids of the aliphatic series liberate all four of the chlorine 
atoms (see Formic and Acetic Acids). 

By this same method a similar compound was obtained with ethyl 
benzoate. Two molecules of this ester and one of zirconium 
tetrachloride were heated with a reflux condenser. There was no 
evolution of hydrogen chloride. Crusts of brilliant crystals formed. 
The composition was found to be ZrCl 4 (C 6 H 5 .C0 2 .C 2 H 5 ) 2 . These 
crystals were unstable in the air, liberating hydrochloric acid. Similar 
compounds were given with other esters, ketones, and aldehydes (611). 

Basic zirconyl benzoates have been prepared by Venable and Blay- 
lock (746) by adding a saturated aqueous solution of benzoic acid 
to a solution of zirconyl chloride. If the solution were cold the pre- 
cipitate was finely granular, forming only after prolonged standing 
and settling slowly. It was evident that the precipitation was only 
partial. When the solutions were heated to boiling the precipitate 
was gelatinous, settling readily and easily washed and filtered. Both 
varieties of precipitate were dissolved by ammonium hydroxide. The 
precipitate was washed free of chlorine by hot water. The white 
precipitate continued to lose water on heating at 100 and darkened, 
hence the analyses were made on air-dried samples. The different 
preparations formed under varied conditions of dilution and washing 
were analyzed. The composition of these was, respectively: 

No. 1, ZrO(OH) 2 .2ZrO(C 6 H 5 .C0 2 ) 2 .6H 2 0; 
No. 2, ZrO(OH) 2 .3ZrO(C 6 H 5 .C0 2 ) 2 .16H 2 0; 
No. 3, ZrO(OH) 2 .6ZrO(C 6 H 5 .C0 2 ) 2 .6H 2 0. 

Apparently no definite compound was formed but a series of basic 
zirconyl benzoates representing various degrees of hydrolysis. These 
may be mixtures or adsorption compounds of zirconyl benzoate and 



ORGANIC COMPOUNDS 115 

the colloidal hydroxide. It is noticeable that the formula assigned 
to No. 1 corresponds to that reported by Rosenheim and Frank (610) 
to the tartrate prepared by them in a somewhat similar manner. This 
may be due to a coincidence of conditions under which the experi- 
ments were made, or may furnish an argument for the existence of 
this as a definite compound formed at a certain stage in the progress 
of the hydrolysis. 

Salicylic Acid. The compound corresponding to the one with 
benzoic acid was prepared (611) by the same method. Zirconium 
tetrachloride was added to an anhydrous ethereal solution of salicylic 
acid and the whole kept at boiling temperature so long as 
hydrogen chloride escaped. Analysis gave the composition as 
ZrCl 2 (OC 6 H 4 . C0 2 . CH 3 ) 2 . The hydrogen of the hydroxyl group com- 
bines with the chlorine to form the hydrogen chloride. It is obtained 
in the form of a white, crystalline crust. When the same reaction was 
tried with salicylaldehyde (the ZrCl 4 being suspended in chloro- 
form) a deep yellow, crystalline powder with the composition 
ZrCl 2 (O.C 6 H 4 .CHO) 2 was obtained. Similar results were obtained 
with other monohydroxy acids and aldehydes and also with ketones, 
but individual mention of these was not made (611). As already 
stated under the appropriate heading, this reaction gives with ali- 
phatic acids compounds in which all of the chlorine is replaced by the 
organic radical. 

A basic zirconyl salicylate was prepared by Venable and Giles 
(748). A saturated solution of salicylic acid was added to a solu- 
tion of zirconyl chloride. A precipitate formed on standing or boil- 
ing. Three preparations were made in which the conditions varied 
more or less, especially as to dilution and amount of water used in 
washing. ' In other words, there was no effort at reproducing the 
exact conditions as to factors in hydrolysis. The analyses gave re- 
sults showing the same product formed in the three experiments. The 
composition was 2ZrH(OH 2 .3ZrO(C 7 H 6 3 ) 2 . This compound was 
less stable than the basic benzoic, decomposition, beginning at 100, 
and the white precipitates were quite black at 160. The samples 
were merely air-dried and contained varying percentages of water. 
This tendency to form one stable basic salicylate shows a decided 
difference from the benzoates. 

The formation of a pyro-racemate (propanonate) has been re- 
ported (65); an acetyl-acetonate (69); and a valerianate (712). 

Hydrocyanic Acid and Thiocyanic Acid. A solution of potassium 



116 ZIRCONIUM AND ITS COMPOUNDS ( 

cyanide gives a precipitate with solutions of zirconyl salts according 
to Weibull (794) . This has not been further investigated. 

When barium cyanide is added in equivalent amount to a solution 
of zirconyl sulphate, barium sulphate is precipitated and zirconyl- 
cyanide remains dissolved. The solution is colorless and easily de- 
composed (794). 

The thiocyanate has been prepared by Hornberger (356) by add- 
ing barium thiocyanate to a solution of zirconium sulphate. After 
removing the precipitated barium sulphate a colorless powder was 
obtained. This was unstable in the air, becoming yellow. Placed 
over sulphuric acid a yellow, amorphous mass, which turned brown 
on the water bath, was left. The analysis gave the composition as 
approximately Zr(CNS) 2 . The value of this work is doubtful as the 
author assumes zirconium to be bivalent. Rosenheim and Frank 
(610) saturated HSCN in alcoholic solution with Zr(OH) 4 and then 
precipitated with ether. The precipitate was white and easily solu- 
ble in water or alcohol. Double salts of the type M 2 H 2 Zr(SCN) 6 
were obtained with pyridine and quinoline. These were crystalline, 
deliquescent, and unstable in air. 

F err o cyanides. The ferrocyanide was investigated by Weibull 
(794), Hornberger (356), and de Boisbaudran (88). The method of 
precipitation was from hot solutions of zirconium salts. Hornberger 
reported a compound, Zr 3 Fe 2 (CN) 12 or 3Zr(CN) 2 .2Fe(CN) 3 . The 
assumption of bivalence for zirconium would seem to make this work 
unreliable. De Boisbaudran (88) stated that ferrocyanide gave a 
yellow precipitate in solutions of zirconium salts even when very acid 
and dilute. Rose (600) reported a precipitate formed with potassium 
ferricyanide. 

Compounds of the Tetrahalides with Organic Radicals, etc. 

The tetrahalides of zirconium form a number of addition com- 
pounds with the amines analogous to those formed with ammonia, also 
with organic bases. Substitution compounds are formed also with 
various organic radicals in which part or all of the halogen is sub- 
stituted. The compounds formed with the tetrachloride have been 
the chief ones investigated. 

In all such reactions in which these tetrahalides are concerned 
water must be absent. Since the tetrachloride reacts with alcohol, 
giving off ethyl chloride when heated and leaving zirconium hydroxide 



ORGANIC COMPOUNDS 117 

(356, 337) , this also can not be used as a medium. Attempts to form 
alcoholates, however, have failed (609). The tetrachloride is soluble 
in ethyl ether with indications of some reaction, since in concentrated 
solutions there are formed yellow crystals which are dissolved on 
further addition of ether and are rapidly decomposed independently 
of the presence of air. Similar crystals are formed by the tetraiodide 
and the analysis indicates the presence of ZrI 4 .4(C 2 H 5 ) 2 O. As alco- 
hol was used in the reaction and the analyses were imperfect, the 
existence of this compound is in doubt. The crystals dissolved in 
water with violent reaction (674). Sometimes the reaction has been 
brought about by suspending the tetrachloride in a medium such as 
chloroform. Carbon tetrachloride might also be used, being inactive 
toward zirconium tetrachloride. Interaction between the vapor- 
ized substances has been seldom tried. The vapor of zirconium tetra- 
chloride was found not to react with certain organo-metallic com- 
pounds, such as mercury ethyl or phenyl. It does react at tempera- 
tures over 300, with methane or acetylene. These reactions have not 
been fully studied. 

Addition Compounds. As double compounds with ammonia are 
formed by passing dried ammonia through an ethereal solution of 
zirconium tetrachloride, so similar compounds can be prepared with 
the amines and organic bases. Matthews (471) prepared a methyla- 
mine compound, ZrCl 4 . 4CH 3 . NH 2 ; ethylamine, ZrCl 4 . 4C 2 H 5 . NH 2 ; 
propylamine, ZrCl 4 .4C 3 H 7 .NH 2 ; pyridine, ZrCl 4 . 2C 5 H 5 N. Pyridine 
hydrochloride, ZrCl 4 .2C 5 H 6 .N.HCl, was prepared by Rosenheim and 
Frank (609) by saturating alcohol in the cold with hydrogen chloride, 
then saturating this with zirconium hydroxide, again saturating with 
hydrogen chloride, and adding to this a concentrated solution of 
pyridine hydrochloride. The micro-crystals obtained were fairly 
stable in the air after washing with alcohol and ether. 

When anilin is added to a solution of zirconium tetrachloride in 
ether a gray precipitate, which seems to be stable when dry, is formed. 
This has the composition ZrCl 4 . 4C 6 H 5 NH 2 (471). In the same way 
was formed a compound with toluidine with similar composition, 
ZrCl 4 .4C 7 H 7 .NH 2 . A gray-brown precipitate having the formula 
ZrCl 4 .2C 10 H 7 NH 2 was given with p-naphthylamine and an analogous 
compound, ZrCl 4 .2C 9 H 7 N, was formed with chinolin (471). A chino- 
lin hydrochloride has been prepared (609). This was microcrystal- 
line and less stable than the corresponding pyridine hydrochloride. 
Its composition was ZrCl 4 .2C 9 H 7 .N.HCl. 



118 ZIRCONIUM AND ITS COMPOUNDS 

Chauvenet (125) prepared addition compounds with pyridine by 
dissolving zirconium tetrachloride in pyridine and evaporating the 
solution, water being excluded. Crystals showing the existence of 
two compounds were obtained. First, there was a compound, 
ZrCl 4 .4C 5 H 5 N, which decomposed at room temperature, more rapidly 
at 50, or in vacuum at 15. The loss by weight ceased when the 
composition ZrCl 4 .2C 5 H 5 N was reached. The latter decomposed at 
70-80. 

Zirconium tetrabromide forms analogous compounds: With ethyla- 
mine, ZrBr 4 . 4C 2 H 5 NH 2 ; with pyridin, ZrBr 4 .2C 5 H 5 N; with anilin, 
ZrBr 4 .4C 6 H 5 NH 2 (471). There is also a pyridin bromhydrate, 
ZrBr 4 .2C 5 H 5 N.HBr, which is much less stable than the tetrachloride 
compound (609). 

Zirconium tetraiodide heated in vapor of ethylamine gives with 
strong evolution of heat a compound, ZrI 4 .6C 2 H 5 .NH 2 . Other ex- 
periments in preparing addition compounds with the tetraiodide have 
been reported (674) , but the methods adopted were open to criticism 
and analytical results unsatisfactory. 

Zirconium thiocyanate also forms compounds with pyridin and 
chinolin analogous to those formed with the tetrahalides. The method 
of preparation is similar (610) . A concentrated solution of thiocyanic 
acid in absolute alcohol was saturated with zirconium hydroxide and 
pyridin thiocyanate added. A yellowish, crystalline precipitate was 
formed. It was extremely unstable. The analyses indicated the com- 
position as Zr(SCN) 6 .HSCN.2C 5 H 6 N. Similarly there was obtained 
with chinolin a compound with like properties to which the formula 
Zr(SCN) 6 .HSCN.2C 9 H 8 N 2 was assigned. 

Hinsberg (337) found that when ZrCl 4 was dissolved in absolute 
alcohol and the solution boiled ethyl chloride was given off and zir- 
conium hydroxide left. When zinc ethyl was added to powdered zir- 
conium tetrachloride and heated to 180 in an atmosphere of carbon 
dioxide butane was given, due doubtless to the presence of some 
water. Rosenheim and Herzmann (611) concluded from their experi- 
ments that ZrCl 4 formed a molecular compound with methyl ether. 
This they were unable to get in a pure state and subject to analysis. 
Molecular compounds were formed with esters by heating with 
ethereal solutions of ZrCl 4 . For instance, when a water-free ethereal 
solution of two molecules of benzoic esters was mixed with an ethereal 
solution of one molecule of ZrCl 4 and boiled with a reflux condenser 
a crust of white crystals formed. These were unstable in the air. 



ORGANIC COMPOUNDS 119 

The analysis gave ZrCl 4 (C 6 H 5 . C0 2 . C 2 H 5 ) 2 . Ketones, aldehydes, and 
esters of various monobasic acids gave the same reaction. In this 
reaction no evolution of hydrogen chloride was observed. 

Peters (540) found that ZrCl 4 did not react at 200 with C 2 H 5 I 
nor with Hg(C 2 H 5 ) 2 . If, however, slight moisture were present the 
reaction ZrCl 4 + 2Hg(C 6 H 5 ) 2 + H 2 = ZrOCl 2 .2HgCl.C 6 H 5 +2C 6 H 6 
took place. This substance was soluble in ether. When heated in a 
vacuum mercury phenyl chloride sublimed. Mercury ethyl and mer- 
cury o-tolyl gave no reaction. 

Jefferson (373) has recorded precipitates as being formed by the 
action of a large number of organic substances upon an aqueous solu- 
tion of zirconium nitrate. Among these were anilin, orthotoluidin, 
xylidin, dimethylanilin, di-ethylanilin, benzylamin, pyridin, piperidin, 
chinolin, etc. The nature of these precipitates is unknown. Hart- 
well (291) also reports a number of such precipitates. 

Kolb (405) added antipyrin to an acid solution of zirconyl nitrate, 
evaporated on a water bath to a syrupy liquid, and then allowed this 
to solidify over a dehydrating agent. The formula assigned on anal- 
ysis of the product was Zr(N0 3 ) 4 .6C 11 H 12 N 2 0. 



Chapter X 

Analytical Methods 

Qualitative 

No flame test is given by zirconium. It can of course be identified 
by the characteristic lines given in the spectrum, but this makes too 
great a demand upon the equipment and skill of the ordinary analyst. 
So delicate a test would doubtless reveal its presence as very widely 
distributed. Pereira-Forjaz (539) has made a spectrographic study 
of Portuguese minerals, finding zirconium in a number of them. 
Microchemical detection has been recommended by Behrens (37), 
who used the strongly refracting crystals of rubidium fluozirconate- 
rubidium fluoride, RbF.Rb 2 ZrF 6 . Sodium-zirconium oxalate crys- 
tals and also those of the corresponding potassium compound have 
been used for this purpose (232, 304) . Since one or both the double 
fluorides and double oxalates may be formed and the properties of 
the crystals differ, these microchemical tests would seem to be unreli- 
able unless definite conditions of formation are maintained. The crys- 
talline form of zirconyl chloride has also been proposed as a test. 
This form varies with conditions of crystallization, and extent of 
hydrolysis. 

Blowpipe reactions for zirconia have been given by Florence (225). 
The behavior of zirconia in borax beads and in those of microcosmic 
salt has been described by Wunder (825) . A number of investigators 
(291, 373, 466) have reported the precipitates given by organic bases. 
Brush (111) found that zirconium salts gave an orange-red with tur- 
meric paper. According to Noyes (528) , the color is more accurately 
described as pink. Titanium gives the same color. Kaserer (383) 
recommended as a color reaction that given by pyrogallol-aldehyde. 
This reagent gives with solutions of zirconium salts a yellow colora- 
tion and on boiling a dirty yellow precipitate and colorless solution. 
The same reaction is given with thorium salts. 

A much used qualitative separation and detection is obtained by 
precipitation of the mixed chlorides with sodium hydroxide in mod- 

120 



ANALYTICAL METHODS 121 

erate excess. The hydroxides of Zr, Fe, Mn, Co, Ni, Ti, and U remain 
undissolved. These are washed and then dissolved in hydrochloric 
acid, the percentage of acid being brought up to 20-32. On shaking 
with ether zirconium chloride is left in the aqueous layer, though 
several shakings with fresh ether may be necessary (528). 

Biltz and Mecklenburg (72) recommended a most delicate and 
useful qualitative test. The solution supposed to contain zirconium 
is strongly acidified with nitric or hydrochloric acid. A few drops of 
sodium phosphate are added and the solution warmed. A white, 
gelatinous precipitate is given when as little as 0.0005 per cent, of 
zirconia is present. No other element known to the authors gave 
such a precipitate in strongly acid solution. Iron, aluminum, the rare 
earths, beryllium, titanium, thorium, and silicon gave no reaction. 
When a mineral is to be examined it can be fused in a soda bead in the 
oxidizing flame, the bead dissolved in excess of hydrochloric acid, 
boiled, filtered, and a drop of the phosphate solution added. The test 
is not applicable if phosphoric acid is present in the mineral. 

In analytical work with zirconium it should be borne in mind 
that all aqueous solutions of its salts have an acid reaction on account 
of the liberation of free acid by hydrolysis. Hence neutralization is 
temporary and even after carrying out the hydrolysis by boiling is 
only approximate. 

Quantitative Determination 

Zirconium in combination with a volatile or organic acid is usually 
determined by direct ignition and weighing as Zr0 2 . Errors may arise 
from two causes. In the first place, certain acid radicals are per- 
sistently retained, even after hours of heating over a blast lamp. 
In the case of chlorides, for instance, a fraction of a per cent of the 
chlorine is thus held. This small amount retained does not seriously 
impair the results in ordinary analyses, but becomes noteworthy where 
strict accuracy is required. The error here is in the direction of 
results that are too high. A second possible error arises from the 
extremely fine subdivision of the zirconia and the ease with which it 
is entrained and carried off by gas currents, such as those resulting 
from the burning of organic acids or the gases from the burner. This 
loss is not prevented by the presence of ammonium compounds as 
maintained by Bailey, but rather accentuated. If nitric acid is the 
one present the volatile radical can be driven off without loss under 



122 ZIRCONIUM AND ITS COMPOUNDS 

the proper conditions. The error here is in the direction of results 
that are too low. Hence this may r in part counterbalance the error 
mentioned above. 

If the zirconium hydroxide has been precipitated by means of 
ammonium hydroxide and so is in the form of hydroxide, there is 
another source of loss which must be reckoned with. Whenever an 
aqueous solution of a zirconium salt stands or is heated hydrolysis 
takes place, so the hydroxide is always present and the necessary 
precautions for this condition must virtually always be applied. It 
has been found that unless the water has been driven off at least to 
1 p.c. or less at a temperature below 300 then, on raising to that 
temperature or higher, the remaining molecules of water are lost 
with the evolution of much energy accompanied by incandescence and 
tiny explosions, thus causing the practical loss of substance. For 
careful work it has been found best to heat in an electric oven or air 
bath at a temperature between 250 and 275 for an hour or so. The 
water in the hydroxide is thus reduced below the danger limit. For 
organic radicals the temperature should be raised stepwise to 250 so 
as to insure the burning taking place at as low a temperature as prac- 
ticable and a reasonably slow evolution of the gases. After the in- 
complete drying or burning the temperature is raised to 300-500 
and the last traces of water driven off at 900-1000. Analyses car- 
ried out in this way will give results higher usually by some tenths 
of a per cent than those obtained by direct and rapid ignition. 

In many cases, as separations, etc., it is desirable that the zir- 
conium be precipitated as hydroxide. Since this colloidal hydroxide 
retains persistently potassium or sodium hydroxide, this precipitation 
should always be done with ammonium hydroxide. The precipitation 
is practically complete and the solvent power of the precipitant when 
used in slight excess is negligible. The other hydroxides exert a slight 
solvent action. For the reason already given the ammonium salts 
formed should be thoroughly washed out before ignition. This is 
more or less difficult according to the condition of the gelatinous pre- 
cipitate. 

Various inorganic and organic substances have been recommended 
as precipitating the zirconium more or less completely from aqueous 
solutions, but on account of the hydrolysis going on in the solution, 
and hence the varying basicity of the salts contained in it, there is 
little certainty as to the nature of the product obtained on ignition 
unless the acid radical can be entirely volatilized, leaving only pure 



ANALYTICAL METHODS 123 

zirconia. Thus oxalic acid has been used (741, 617, 621) ; lactic acid 
or salicylic acid (38, 746) ; thiosulphate (686, 325) ; sodium azide 
(157) ; acetic acid (276) ; chromate (276, 748) ; alkaline iodate (169, 
102, 751); sulphurous acid (31). 

The precipitation with phosphoric acid or an alkali phosphate has 
been frequently made use of in certain separations, determining the 
zirconium as phosphate, but the composition of this precipitate varies 
according to the extent of the hydrolysis. It has been chiefly used 
where the amount of zirconium present is quite small and the varia- 
tions in composition negligible. The precipitate approximates in com- 
position ZrP 2 T (677) . The use of the empirical factor Zr = 0.3828 
has also been suggested (216, 516) . Precipitation by means of sodium 
subphosphate has also been suggested (412) . 

Separation from Other Elements 

Precipitation by means of ammonium hydroxide furnishes a 
method for the separation of zirconium from a number of other ele- 
ments not precipitated by this reagent in dilute solutions. The col- 
loidal nature of zirconium hydroxide and its strong adsorptive power 
must, however, be kept in mind. In some cases the thorough wash- 
ing out of alkalies and other substances is difficult even with pro- 
longed washing. Aluminum, manganese, the iron group, titanium, 
and uranium are precipitated along with the zirconium. 

The separation from aluminum by means of an alkali iodate has 
been investigated (169, 102). The precipitation is quantitative in 
the presence of an excess of the reagent and also of nitric acid. lodic 
acid may be used instead of the iodate (751). While this method 
will separate zirconium from a number of other elements, it can not 
be relied on for separation from thorium and titanium (412) . 

A complete and satisfactory separation from iron has been the 
object of much investigation, since this element is the most usual 
concomitant of zirconium and must be removed for a number of in- 
dustrial uses. A complete list of methods used or recommended would 
have little practical bearing, as many of them are out of date and 
abandoned. For the remainder only the general principles involved 
can be indicated. 

The weighed mixture of oxides may be heated in a current of 
hydrogen (595, 272, 273, 164, 165) or of phosgene (762) or the iron 
may be titrated (684) . The mixed oxides may be treated with hydro- 



124 ZIRCONIUM AND ITS COMPOUNDS 

gen chloride (312). The neutral solution may be treated with sul- 
phur dioxide or alkali sulphites added (47, 319, 31), by- adding am- 
monium sulphide in the presence of tartaric acid (573, 118, 356, 238, 
401), by treatment with hydrogen peroxide or sodium dioxide (18, 
238, 188, 191), by precipitation with nitroso-naphthol (401), by pre- 
cipitation with thiosulphate (686, 326, 467). Electrolytic dissocia- 
tion has also been investigated (144, 338). The separation of zir- 
conium from iron in the presence of titanium and also when both 
titanium and thorium are present has been investigated (188, 189, 
190). For separation from titanium a number of methods have been 
proposed (552, 326, 684, 172, 21, 16, 173, 188, 189, 190, 191, 108). 
Some of these make use of hydrogen peroxide as the precipitant. This 
precipitates both and the titanium may then be determined colori- 
metrically (188, 191, 6). Ammonium salicylate, sodium acetate, and 
acetone have also been used. Fractional precipitation by means of 
ammonium hydroxide at boiling temperature has been used for sepa- 
ration of titanium and columbium. The use of oxalic acid or alkaline 
oxalates has been investigated (246), but has been found unreliable 
if sulphuric acid is present (617). 

Various methods have been suggested for separation from thorium 
(326, 246, 173, 563, 368, 190). 

In its natural occurrence zirconium is always associated with 
silicon. The separation here is by the usual method of heating with 
hydrofluoric acid. There is a necessary precaution, however, namely, 
that an excess of sulphuric acid must always be present; otherwise 
some zirconia will be lost (784). Some of the sulphuric acid radical 
is also persistently retained and the ignition must be carefully and 
thoroughly carried out. 

Cupferron, which is the convenient name for the organic com- 
pound nitroso-phenyl-hydroxylamme-ammonium, has been proposed 
as a precipitant for the separation and determination of zirconium. 
It was found that zirconium could be quantitatively precipitated by 
it in acid solutions (615). At first the amount of acid (sulphuric) 
which might be present could amount to as much as 5-7% p.c. by 
volume (705), and this was later confirmed (218). The method was 
used successfully by Brown (106), and Lundell and Knowles (458) 
have recently shown that 40 p.c. of sulphuric acid may be present. 
Tartaric acid also does not interfere. Nitric acid decomposes the 
reagent. The iron must first be removed by precipitation with am- 
monium sulphide in the presence of tartaric acid. For separation 



ANALYTICAL METHODS 125 

from aluminum the solution must be highly acid and the presence of 
tartaric acid is desirable. The presence of platinum or boric acid 
does not interfere, but that of phosphoric acid introduces a disturbing 
effect. The method is recommended as most exact. On ignition of 
the precipitate zirconia is obtained but the usual precautions to pre- 
vent loss must be observed. See also (40). 

The method involving the use of phenylhydrazine has been recom- 
mended (4). This and the cupferron method of analysis, as well as 
the phosphate and the thiosulphate, have been comparatively investi- 
gated (467, 333). 

An investigation of the various methods for determining zirconium 
has been made by Lundell and Knowles (458, 460). Objections to 
previous methods are detailed. The methods especially tested are 
those of Kelly and Meyers (387), Ferguson (216, 217), Johnson (375, 
376), Travers (710), and Hillebrand (333, 334). A mode of pro- 
cedure is recommended for the separation and determination of zir- 
conium, especially in steels. The final precipitation is by cupferron, 
giving zirconia and titanic oxides on' ignition. The titanium is deter- 
mined colorimetrically. 



Chapter XI 

Technical Applications of Zirconium and Its Compounds 

Precious Stone 

The earliest use made of a compound of zirconium was that of 
the natural silicate as a precious stone. It was known under the 
names zircon, jargon, and hyacinth, and in early times was also sup- 
posed to have medicinal value. The use of the name hyacinth among 
the ancients was confusing as, besides the zircon, it sometimes meant 
the carbuncle and also a dark amethyst. The zircon, known by 
lapidaries commonly as the Ceylon zircon or jargon, was regarded as 
distinct from the hyacinth and was usually colored fire-red, yellow, 
yellowish-green, or gray. The hyacinth was distinguished as Oriental 
hyacinth. Its color was deep red with a touch of brown or some- 
times of orange-red. Zircons show a great variety of colors from 
colorless to red, brown, yellow, green, gray, white, pink, and blue, 
besides intermediate tints. They may be translucent but ordinarily 
are opaque. 

On account of its hardness (7.5) the zircon is cut with diamond 
powder or emery. It is cut in the rose, table, or brilliant form. The 
value depends chiefly upon the purity of the color. On account of 
its lustre and hardness it has been substituted for the diamond. In- 
deed, at one time it was supposed to be an inferior variety of dia- 
mond. It has been used in jewelling watches and as supports for 
the knife edges of fine balances. There is little demand for it at 
present in jewelry except in the case of fine crystals of pure color. 
At one time it was supposed to be peculiarly appropriate and was 
much used in mourning jewelry. The artificial preparation of zircons 
has been attempted (168, 182, 183). 

Oxy-hydrogen Light 

The brilliancy of the light given off by zirconia in the oxy-hydro- 
gen flame was first observed by Hare (285) in 1820 in his effort to 
fuse it. After the development of the Drummond limelight it was 

126 



TECHNICAL APPLICATIONS OF ZIRCONIUM 127 

suggested that zirconia be used as a substitute for the lime, offering 
the advantages of slight absorbing power for carbon dioxide or water. 
In 1868 du Motay (507, 508) used it in one of the lamps lighting the 
Tuileries. Napoleon III was so pleased with the result that he ordered 
its installation in all of the lamps illuminating the court and gardens. 
The zirconia light attracted much attention on the part of inventors 
and others (66, 117, 167, 199, 287, 404, 451, 482, 535, 545, 657, 700, 
740). On account of the purity of the light and the high emissive 
power of the zirconia it was recommended for scientific use (433), 
such as polariscopes, spectroscopes, etc., but this more especially 
refers to the next form. 

Gas Mantles 

With the introduction of the Welsbach mantles interest in the 
Drummond light diminished. The first incandescent mantles made 
by Welsbach in 1880 consisted essentially of zirconia (810). Later 
this was largely substituted by the oxides of thorium and cerium, 
which have a higher emissive power. Zirconia is used in admixture 
with these and other rare earths (679). 

Incandescent Filaments 

A number of attempts have been made to use metallic zirconium 
in the form of filaments in incandescent electric lamps. Its electrical 
conductivity and high fusing point should render it quite suitable for 
this purpose. Korolkow (411) has made an examination of the elec- 
trical resistance, emissive power, and expansion coefficient of zir- 
conium filaments but such determinations are considerably affected by 
the presence of even small amounts of impurities. One difficulty 
which has to be met is the preparation of pure zirconium on a com- 
mercial scale and at a reasonable cost. Most of the experiments with 
zirconium filaments have been carried out with the more or less impure 
metal, sometimes associated with the carbide, which itself has been 
said to be unsuitable for the purpose. The properties of zirconium 
seem to favor its use as a substitute in part for tungsten should the 
difficulties in the way of its commercial production in a pure form 
be overcome, and its abundance and wide distribution would speedily 
make it replace the more costly metal. [See also Alloys.] A number 
of patents bearing on the manufacture of the filaments have been taken 
out (418-423). [See also Weber (769) and Wedding (771, 772).] 



128 ZIRCONIUM AND ITS COMPOUNDS 

According to Meyer (486), investigators who have succeeded in pro- 
ducing malleable zirconium state that it has remarkable properties 
which fit it for use in the chemical laboratory as a substitute for 
platinum. So far nothing has been published on this subject. 

Reduction of Metals 

A patent has been granted (385) for the use of ores containing 
zirconium in extracting gold, platinum, and other noble metals. The 
supposition is that zirconium in the metallic state is the active agent. 
Neither the chemistry nor the object of this patent is easy to unravel. 

There is another patent (213) for the use of zirconium, its alloys 
with magnesium or aluminum, its carbide or phosphide, as a means 
of reducing other metals or forming alloys with them. The reaction 
is said to be exothermic and hence proceeds from its own heat after 
starting. 

Alloys 

Various alloys of zirconium have, been formed. The ferro and 
nickel alloys promise the greater usefulness. Bronzes have also been 
made. Cobalt, aluminum, and magnesium alloys have been placed on 
the market. Ferro-zirconium has been recommended in steel manu- 
facture for removing oxygen and nitrogen. It has been offered com- 
mercially, containing 40-90 p.c. of zirconium. Small percentages of 
titanium have also been introduced. 

The technically important alloys, chiefly those with metals of the 
iron group, are mentioned under Patents. In the earlier attempts 
to prepare the pure metal, certain alloys or zirconides, which led to 
confusion in the descriptions of the metal, were obtained. With 
aluminum there were made preparations, some crystalline, which con- 
tained varying proportions of aluminum (713, 714, 230, 489, 776). 
Such formulas as Zr 3 Al 4 and ZrAl 2 have been assigned to these. Sim- 
ilar alloys were formed when magnesium was used instead of alumi- 
num. There seems to be no tendency to alloy with metals of the 
alkali nor alkaline earth groups, nor with lead or copper. The alloys 
are often formed by thermo-electric or alumino-thermic processes. 

It is claimed that these alloys are not subject to oxidation and 
that they are very resistant to chemical reagents. The alloys have 
a metallic lustre and some of them take a silvery, steel-like polish. 
They are readily malleable and may find a use as filaments for 



TECHNICAL APPLICATIONS OF ZIRCONIUM 129 

incandescent lamps. Such filaments are claimed to have the power of 
selective radiations; in other words, emit more light than corresponds 
to the temperature to which they are heated by the electric current. 
This implies a considerably lower wattage per candle power than is 
now required by the average metal filament lamp (486). Analysis 
of one such alloy shows zirconium, 65 p.c.; iron, 26 p.c.; titanium, 
0.12 p.c.; and al, 7.7 p.c. These alloys are produced by reduction 
with finely divided aluminum, together with the mixed oxides of iron, 
titanium, or whatever metal it is desired to introduce into the alloy. 
Or they may be produced by heating the mixed oxides in a graphite 
crucible in an electric furnace, using either zircon or zirkelite as a 
source of zirconium (486). 

For use as a scavenger in casting steel a 20 p.c. ferro-zirconium is 
recommended in an amount equal to 1 p.c. of the weight of steel 
treated. 

Furnace Applications 

Mixed with good conductors zirconia is said to improve furnace 
electrodes (759). On account of its low conductivity for both heat 
and electricity it can also serve as an insulating material. It is fur- 
ther used to replace thorium nitrate for coating the iridium bar and 
preventing the loss of iridium in the Heraeus furnace. 

The oxide, zirconia, possesses physical and chemical properties 
which make it available for a variety of industrial uses. Among 
these properties are its high melting point and its low heat con- 
ductivity. On account of its low coefficient of expansion it with- 
stands sudden changes of temperature. Its porosity is low, so that 
it is practically impervious to liquids. It is inactive toward most 
chemicals and is scarcely attacked by strong acids or alkaline fusion 
mixtures. It does not, however, resist the action of hydrofluoric acid 
and fluorides. Fused bisulphates also act upon it to some extent. 
It is, however, quite stable in the presence of most fluxes and slags. 

As binding material, various organic substances, such as starch, 
organic acids, glycerine, tar, etc., have been recommended; also mag- 
nesia, phosphates, and borates. Since the native zirconia from Brazil 
is reasonably pure, it may be used direct with no other than mechani- 
cal treatment. Native zirconia begins to fuse at 1800. For use in 
laboratories and chemical manufacture it is first purified. The chief 
impurities are iron, titanium, and silicon. 

Working tests show that zirconia has much greater life duration 



130 ZIRCONIUM AND ITS COMPOUNDS 

as a lining for furnaces than other refractories. In Germany experi- 
ments were carried out in a closed hearth steel furnace and it was 
found that the zirconia lining was good for eight months' use without 
renewal. This is several times longer than the usual life. Because 
of the low thermal conductivity the thickness of the lining could be 
reduced one-half, a two-inch lining being equal to four inches of 
chamotte. Furthermore, there was a saving of one-half in main- 
tenance costs. In casting molds it shows a high resistance to steel, 
copper, brass, and bronzes. 

It may be used as a protective coating for ordinary firebrick ex- 
posed to the action of acids or slags. In such cases, sodium silicate 
serves as a binding material; air-slaked lime may also be added. If 
it is desirable to increase the porosity and decrease the density organic 
substances or volatile salts may be added and burned out in the 
firing. It is of course detrimental to use a binder which may cause 
softening at comparatively low temperatures. 

Refractories 

As a refractory, zirconia has also been used in making crucibles, 
muffles, pyrometer tubes, and for a variety of chemical wares. Com- 
bustion tubes made of it are said to be gas-tight up to 1000. Cru- 
cibles and combustion tubes of zirconia have been used in the research 
laboratory of the Royal Berlin Porcelain Factory, as they possess 
great strength and also conduct electricity. They withstand high 
temperatures and sudden changes. Zirconia crucibles have been used 
for determining the melting points of pure iron, tungsten alloys, and 
platinum. Such ware can be plunged in water while red hot without 
injury. (For its use as a refractory see 13, 14, 278, 588, 589, 605, 624, 
625, 626, 178, 290, 572.) 

Enamels 

Zirconia is also used as an opacifying agent in enamels and a 
clouding agent in glass as a substitute for the costly stannic oxide and 
the poisonous compounds of antimony and arsenic. For this purpose 
it should be quite free from iron, and a number of processes have been 
worked out and some patented. General references follow (266, 267, 
288, 336, 413, 430, 431, 432, 166, 592, 658, 675, 802, 762). The in- 
creasing demand for tin for other purposes and the limited supply 
may render this substitution necessary. According to some author- 



TECHNICAL APPLICATIONS OF ZIRCONIUM 131 

ities, the zirconia has less covering power than stannic oxide. For 
cheaper ware native zirconia may be used, or ground zircon which 
has been treated with hydrochloric acid, then caustic soda, and finally 
leached with acidulated water. This would only partially remove the 
iron present. 

Glass 

The use of zirconia as a clouding agent for glass has been men- 
tioned above. A thorough comparison with stannic oxide in this 
application apparently has not been worked out. The addition of a 
small amount of zirconia to "vitreosil" or silica glass is said to in- 
crease the tensile strength and resistance to bending or breaking, and 
to diminish the tendency to devitrification. The temperature at which 
the ware softens is practically unchanged. The appearance is not 
improved (3, 90, 494, 655, 702, 823). 

Textile Applications 

Zirconium salts, as the hydrated sulphate or the acetate, have 
been used as a weighting filler for silk (429, 594, 678). The weight 
may be increased up to 50 p.c. Stannic salts are ordinarily employed 
for this purpose. 

Various zirconium compounds are also used as mordants in dyeing 
(26, 642, 813) and in the preparation of lac dyes (642). Zircon white 
(799) is used as a pigment, having good covering powers and being 
unaffected by chemical agents (84). A patent has also been issued 
for the preparation of a zirconyl tannate (573) . 

It may also find a use as substitute for sodium tungstate or stan- 
nate in rendering cloth non-inflammable. 

Colloidal Applications 

The colloidal properties of the hydroxide have been compared 
with those of other hydroxides and its use suggested in the purifica- 
tion of water (67, 68, 71). 

Medicinal 

As "Kontrastin" it may be substituted for bismuthyl nitrate as a 
lining substance for the stomach, etc., in X-ray observations and 
radiographs. It has the advantage of being non-poisonous (803). 
This has been patented. 



132 ZIRCONIUM AND ITS COMPOUNDS 

Abrasive 

The carbide has been recommended as a polishing agent, abrasive, 
and for glass cutting (798, 801). 

Chlorinating Agent 

Willgerodt (816) has suggested the use of the tetrachloride as a 
chlorinating agent. 



Chapter XII 
Patents 

1914. Arnold (11). U. S. Patent 1,121,890. 

Utensils made of zirconia. The oxide is subjected to a high 
pressure. After withdrawing the pressure the substance is turned 
into a paste by means of a suitable fluid (water, alcohol, or the 
like) , cast in molds, dried, and burned. The articles do not crack 
nor fissure. They may be glazed with titanium oxide, alumina, 
or silica. Similar articles made of thoria or the rare earths may 
be glazed with zirconia. The melting point of the glaze may be 
so arranged by mixing such oxides as to be a few hundred degrees 
over the highest temperature to which the article is to be exposed. 
The glaze is dried and burned on in a second heating. 

1915. Askenasy (12). U. S. Patent 1,158,769. C. A. 10, 255. 
Method of producing zirconia free from iron. This consists 

in heating the zirconium salt of a mineral acid (containing such 
impurities) under pressure to a temperature above the boiling 
point. Zirconium hydroxide separates out in an easily-filtered 
form and the impurities are left in the acid solution. 
1909. Badische Anilin u. Sodafabrik (17). Ger. Patent 237,436. 

C. A. 6, 1507. 

This patent refers to the preparation of zirconium nitride and 
its purification by treating with acid or oxidizing agents. 
1920. Barton (28). U. S. Patent 1,342,084. C. A. 14, 2140. 

Zirconium cyanonitride. Ore mixed with about 20 per cent 
of coke is heated in an electric furnace (with a nitrogen-bearing 
gas?). This yields a product containing Zr 82-84 per cent, C 3-5 
per cent, and N 8-10 per cent. Cold 5 per cent H 2 S0 4 may be 
used to remove excess of iron. The product is golden yellow to 
bronze in color and has a specific gravity of 5.95-6.35. 
1920. Barton (29). U. S. Patent 1,351,091. C. A. 14, 3301. 

Zirconium oxide. This oxide may be produced from baddeley- 
jte pr zircon by melting with carbonaceous material, such as coke, 

133 



134 ZIRCONIUM AND ITS COMPOUNDS 

to form zirconium cyanonitride and the resulting product then 
heated with salt cake or niter cake. 
1914. Bohm (85). U. S. Patent 1,099,110. C. A. 8, 2653. 

This describes the fusion of zirconia in caustic alkali by means 
of an electric current. The zirconia is mixed with caustic alkali, 
which acts as an initial conductor and is later volatilized. 

1914. Bosch and Mittasch (91). U. S. Patent 1,102,715. C. A. 8, 

3353. 

Purification of the nitride. Heat with air at 700 to burn out 
any carbon. Treat the residue with H 2 S0 4 or HC1 or FeCl 3 
solution to decompose other impurities without decomposing the 
nitride. K 2 Cr 2 7 , Mn0 2 , and a flux may also be used in oxidiz- 
ing the impurities. 
1919. British Thomson-Houston Co. (103). Brit. Patent 139,247. 

C. A. 14, 1960. 

Alumino-thermic extraction of zirconium. Finely divided 
Al (80-200 mesh) mixed with 10 per cent fine flaky Al (60-200 
mesh) is briquetted with zirkite, Na 2 Si0 3 serving as binder. The 
slag may be used as an abrasive. 

1915. Brown and Cooper (107). U. S. Patent 1,151,160. 
Production of ferro-zirconium. This alloy contains 40-90 p.c. 

of zirconium. It may also have 60-90 p.c. of zirconium along 
with an iron-group metal. It is malleable and ductile. The 
oxides of zirconium and iron (and titanium) are mixed with 
aluminum and the mixture ignited. 

1916. Campbell and Carney (114). U. S. Patent 1,182,880. C. A. 

10, 1918. 

Separation of zirconium and thorium from the rare earths. 
The pyrophosphates of zirconium and thorium are insoluble in 
dilute acids. The pyrophosphates of the rare earths, except eerie 
salts, are soluble. Reduction by means of H 2 S0 3 renders the 
latter soluble also. Zirconium is then separated from thorium 
by the solubility of the oxalate in oxalic acid. 

1917. Cooper (150). Can. Patent 179,121. C. A. 11, 3234. 
Production of an alloy for cutting tools containing 8-15 p.c. of 

zirconium with 50 p.c. or more of nickel. It is free from iron or 
carbon and will not burn when cutting at high speed or grinding. 
The wear is small and the tool remains white. 
1917. Cooper (151). Brit. Patent 112,259. C. A. 12, 1286. 

Production of an alloy for cutting tools, electrical resistance, 



PATENTS 135 

etc. It contains 2-40 p.c. of zirconium, the remainder being nickel 
or cobalt. One or more metals of the chromium group may be 
added. The alloy may also contain up to 35 p.c. of molybdenum; 
up to 25 p.c. of zirconium, the remainder being nickel or cobalt; 
or up to 25 p.c. of tungsten and the remainder nickel and zir- 
conium. These alloys are made by the thermo-aluminic method, 
the reactions taking place between mixtures of the oxides of 
nickel, zirconium, etc., or their ores and aluminum. 

1918. Cooper (152). Can. Patent 185,436. C. A. 12, 1762. 

Production of an alloy containing zirconium, nickel, aluminum, 
and silicon, which is especially adapted to cutting. The addition 
of silicon greatly increases the hardness. Zirconium modifies the 
physical and structural characteristics. A scleroscopic hardness 
of 65-75 is easily reached. Tungsten may be added. 

1920. Cooper (153). U. S. Patent 1,350,359. C. A. 14, 3219. 

Alloy for cutting tools. This may be used for high speed 
cutting tools and is composed of Ni 76.2 p.c., Zr 4.8 p.c., Al 2.0 
p.c., Si 5.9 p.c., W 3.8 p.c., Fe 6.8 p.c., and C 0.29 p.c. 

1920. Cyclops Steel Co. (159). Brit. Patent 151,981. C. A. 15, 667. 
Corrosion-resisting steel alloy. This contains Fe of low car- 
bon content, Si and Zr or other metal of the C group. The per- 
centage of Si and Zr together is preferably about 2. Cr or Cr, 
Ni, and Mn may be added, the percentage of Cr being about 
3-7 and of Ni about 5-20. In some cases about 0.3 p.c. Cu may 
be added. 

1920. Dantsizen (166). U. S. Patent 1,343,040. C. A. U, 2403. 

Porcelain containing zirconium oxide. Zr0 2 to the amount of 
about 15 p.c. is used in porcelain to improve its strength and 
electrical resistance at high temperatures. The porcelain may 
be formed of clay, 45; feldspar, 35; and zirconia, 15 parts. 

1914. Dennis (175). U. S. Patent 1,115,513. C. A. 9, 27. 

This describes a method for separating zirconium from the rare 
earths by electrolysis. The aqueous solution of the nitrates is 
subjected to the action of an electric current while maintaining 
the cathode surface substantially free from an adherent deposit. 
The current is at or above the lowest decomposition voltage of 
the first product desired. The deposition is fractional. The 
separate portions are removed as formed and the remainder is 
subjected again to the action of the current. The mercury 



136 ZIRCONIUM AND ITS COMPOUNDS 

cathode is kept clean by forcing air through the mercury so as 
to agitate it and prevent any formation on the surface. 
1913. Ehrich, Gratz, and Podszus (207). Ger. Patent 289,063. 

C. A. 10, 2438. 

Production of filaments. Pure zirconium is ground to a fine 
powder. It is then worked into an emulsion with a liquid, such 
as C 6 H 6 , CS 2 , etc., and formed in filaments by pressure. These 
are heated by electricity in a non-oxidizing atmosphere close to 
the melting point and this temperature is maintained for a long 
time. 

1918. Elektro-Osmose Gesellschaft (208). Brit. Patent 113,777. 

C. A. 12, 1415. 

Use in enamels. Colloidal zirconium hydroxide as hydrosol is 
applied as a coating, dried, and fired at a temperature below the 
melting point. A small amount of water-glass may be added if 
desired. 
1902. Escales (213). Ger. Patent 145,820. C. B. 1903, II, 1155. 

A method of preparing metallic zirconium or its alloys. This 
involves the use of rare-earth metals or mixtures of their alloys 
with magnesium or aluminum. Carbides or phosphides of these 
metals may also be used, or mixtures of these, such as may be 
obtained by the electric melting of the phosphates, etc., mixed 
with carbon. The reduction process is endothermic. 

1919. Eyer (215). U. S. Patent 1,314,861. C. A. 18, 2748. 

A clouding composition for enamels. Zirconia is apt to pro- 
duce spotted enamels and also they may become dull or tarnished 
on firing. Ordinary zirconium borate is free from these defects 
but has poor covering capacity. A highly basic zirconyl borate, 
as Zr0 2 . 2B 2 3 -f- 4Zr0 2 , has much greater covering capacity and 
is free from the defects mentioned. The process consists in fusing 
together 7 parts of raw zirconia, about 3 parts of B 2 3 , about 2 
parts of cryolite, and 5 parts of NaN0 3 , allowing the mass to cool 
and powdering it. 

1908. General Electric Co. (239). Brit. Patent 5,415. Soc. Chem. 
Ind. 28, 83. 

Filaments for incandescent lamps. Filaments or other con- 
ductors are made from zirconium oxalate with just enough zir- 
conium on heating to the necessary temperature without leaving 
any residual carbon. No binding material is necessary, since the 
oxalate forms a tenacious paste which can be squirted. The 



PATENTS 137 

oxalate may be prepared by precipitating a hot zirconium nitrate 
solution with ammonium oxalate. It resembles starch paste. 
The heating may also be applied to the production of alloys of 
zirconium. 

1917. Glazebrook, Rosenhain and Rodd (247). Brit. Patent 112,973. 

C. A. 12, 1111. 

This covers a basic zirconyl sulphate and a basic zirconyl 
chloride. The sulphate is obtained by adding caustic alkali, 
such as NH 4 OH or NaOH, to an acid solution of Zr(S0 4 ) 2 until 
a permanent precipitate begins to form and then allowing the 
precipitation to proceed of itself. This basic sulphate may be 
converted into tha oxide by ignition. Likewise a basic zirconyl 
chloride Zr 5 8 Cl 4 .22H 2 may be prepared, dissolved in water, 
H 2 S0 4 added and a sulphate 5Zr0 2 .2S0 3 .14H 2 formed. 

1920. Gordon (250). U. S. Patent 1,340,888. C. A. 14, 2242. 

Preparation of Zr0 2 from ore. Ore is fused with 3-4 times its 
weight of Na 2 0, NaOH, Na 2 C0 3 or CaO and 3-4 times its weight 
of NaCl or CaCl 2 . Fusion at 1000-2000 for 30-60 minutes, 
poured, cooled, pulverized. Si0 2 separated with H 2 S0 4 , filtered, 
precipitated as Zr(OH) 4 and other bases by NH 4 OH or other 
alkali. 

1917. Grenagle (258). U. S. Patent 1,248,648. C. A. 18, 361. 

Ferro-zirconium alloys. The object is to produce an alloy of 
zirconium, which, because of its selective radiation, will be use- 
ful for filaments in electric lamps, and in the manufacture of 
transformer elements. The process is one of co-reduction of 
compounds containing zirconium and iron, best in the presence 
of a titaniferous compound. This reduction may be brought 
about by aluminum. Thus 3Zr0 2 + 3Fe 2 3 + 5A1 2 = 
3ZrFe 2 + 5A1 2 3 . This reaction may be carried out by heating 
the mixed oxides with aluminum in a graphite crucible with the 
electric current or oxy-acetylene flame. 

1920. Grenagle (259). U. S. Patent 1,334,089. C. A. 14, 1266. 

Zr-Nb-Ta alloy. Formed by heating the mixed oxides in an 
electric furnace. It contains Zr 6.8 p.c., Nb 53.5 p.c., Ta 39.7 
p.c. It is not attacked by acids or alkaline solutions, does not 
oxidize or vaporize at white heat, and combines with C to form 
carbides which are hard and brittle. The alloy is malleable, duc- 
tile, and somewhat resembles Pt but is slightly yellowish. 

1904. Guertler (269). Ger. Patent 182,200. C. B. 1907, I, 1518. 



138 ZIRCONIUM AND ITS COMPOUNDS 

A method of changing difficultly crystallizable substances into 
crystalline form. The compounds or mixtures are dissolved in 
fused alkaline metaborates (e.g., NaB0 2 ) and this solvent driven 
off by heat, which is readily done at 850-950 in a platinum 
crucible. LiB0 2 is volatilized in 8 hours, NaB0 2 in 4 hours, and 
KB0 2 in 1 hour. Zircon can be crystallized in this way. 

1909. Gustrow (271). Ger. Patent 189,364. 

This refers to the use of zirconia as an opacifier in enamels. 

1912. Hansen (283). U. S. Patent 1,026,392. C. A. 6, 1882. 

Improvement in incandescent lamp filaments. This consists 
in forming threads made of refractory powder held together by a 
binder composed essentially of gelatinous zirconium oxalate, de- 
composable into a refractory oxide, and heating said threads in 
an inert environment to convert the oxalate into oxide and to 
consolidate and sinter the refractory metal. 

1914. Hansen (284). U. S. Patent 1,084,629. C. A. 8, 871. 

Improvements in zirconium lamp filaments. The process con- 
sists in mixing carbon with gelatinous zirconium oxalate, shaping 
the mixture into threads, then heating in an inert and rarefied 
atmosphere to produce coherent conductors of pure zirconium. 

1912. Havas (310). Ger. Patent 262,009. C. A. 7, 3650. 

This refers to the production of iron-free zirconia for enamels. 
A weak hydrochloric acid solution of a zirconium salt is heated 
in a closed vessel to temperatures above the boiling point (at 
ordinary pressure). Zirconium hydroxide separates out, is fil- 
tered, centrifuged, and washed. This is snow-white on ignition. 
Other acids besides hydrochloric may be used. 

1913. Havas (311). Brit. Patent 9,153. C. A. 8, 3355. 

This is apparently the same as preceding, only more detailed. 
The temperature to which the acid zirconyl chloride solution is 
heated is given as 200. 
1905. Heraeus.(318). Ger. Patents 156,776 and 179,570. 

These refer to the making of chemical apparatus out of zir- 
conia. 

1914. Herzfeld (330). Ger. Patent 290,878. Soc. Chem. Ind. 35, 

634. 

A process for obtaining pure Zr0 2 from zirkite. The ore with 
excess of lime and carbon is heated short of complete reduction 
of the lime. The product is then treated with hydrochloric acid, 



PATENTS 139 

the silica removed, and the zirconyl chloride purified. Calcium 
carbide may be used in place of carbon. 

1920. Hisamoto (341). U. S. Patent 1,345,441. C. A. 14, 2687. 

Drawing filaments. Zr is surrounded by Zr0 2 , enclosed in a 
tube of metal as Ni, and contents drawn to a filament. The tube 
and oxide are dissolved away with acid. 

1920. Hutchins (364). U. S. Patent 1,362,316. C. A. 15, 583. 

Refractory material. Such a material suitable for furnace lin- 
ings, crucibles, or muffles is formed of a burnt mixture of zirconia 
and alumina. 

1920. Hutchins (365). U. S. Patent 1,362,316. C. A. 15, 583. 
Refractory material. A mixture of burnt zirconia and chro- 

mite is used as a refractory material for furnace construction and 
similar uses. 

1914. Jost and Plocker (380). Ger. Patent 285,981. C. A. 10, 1087. 
Preparation of the silicide, oxide, and salts. Pulverized zircon 
is mixed with 1 1/9 times its weight of coal and heated to white- 
ness. The silicide is formed and carbon dioxide escapes. The 
resulting mass is treated with dilute mineral acid and filtered 
away from the carbon. The salt is thus freed from silica and on 
ignition the oxide is obtained. It is useful for enamels. 

1921. Kaiser (381). Can. Patent 207,290. C. A. 15, 667. 

Alloys having high melting point and ductile properties are 
produced from such metals as Cr, W, V, Th, Zr, and Ru by add- 
ing one metal to another, which is used as a base, and adding a 
small amount of a second metal, which has a catalytic action, 
before sintering the mixture. 

1887. Keeport (385). Ger. Patent 43,231. Ber. deutsch. chem. Ges. 
21 c, 458. 

Zirconium is described as having a great affinity for gold, 
platinum, etc. Zirconiferous ores are added to the material car- 
rying the precious metals and the mixture is treated with a sol- 
vent. The undissolved material is separated and the precious 
metals precipitated. (This is seemingly meaningless.) 
1913. Knofler (397). Ger. Patent 285,934. C. A. 10, 1087. 

This refers to the manufacture of refractory vessels. Pure zir- 
conia mixed with some water is shaped by high pressure into 
suitable forms. Upon subsequent burning in furnaces at 1400- 
1600 the articles acquire the requisite solidity and hardness with 
contraction. There is no sintering. The vessels may be heated 



140 ZIRCONIUM AND ITS COMPOUNDS 

"to 2000 and above for a long time without fusion. Thoria and 
the rare earths may be mixed with the zirconia. 

1913. Knofler (398). Ger. Patent 287,554. C. A. 10, 2134. 

This is an addition to the preceding patent. Zirconia, or a 
mixture with thoria, without binding material is subjected to high 
pressure. After relieving the pressure the product is finely ground 
and then stirred with water or alcohol and poured into the forms, 
dried, and burned. The articles are readily removable from the 
forms. There are no cracks on drying or burning. The vessels 
are tight and not easily fractured. 

1907. Kuzel (418). U. S. Patent 871,599. C. A. 1, 1930. 

A method of converting elements into the colloidal state. This 
consists in first comminuting the zirconium and then treating the 
same under heat and agitation alternately with dilute solutions 
of an acid character, and then dilute solutions of a non-acid 
character, and between such treatments washing with pure in- 
hibition liquid. The acid solutions may be organic from 0.5-20 
p.c., or mineral acids or salts having an acid reaction. The basic 
may be 0.5-10 p.c. caustic alkali solutions, ammonia, or organic 
bases. 

1907. Kuzel (419). Ger. Patent 204,496. C. A. 3, 881. 

A process for making alloys of definite composition and objects 
therefrom. One constituent only need be in colloidal form (i.e., 
zirconium) and as many others as desired in the form of crystal- 
loids, such as salts, oxides, hydroxides, acid salts, and halogen 
compounds. These latter are combined with the colloid by suit- 
able means, such as precipitation of the colloid with an electro- 
lyte until a plastic mass. This method is applicable in the 
manufacture of filaments. 

1908. Kuzel (420). U. S. Patent 899,875. C. A. 3, 288. 

A process for peptizing coagulated colloids of refractory ele- 
ments free from carbon. This consists in treating such colloids 
with solutions of alkaline reaction and stopping such treatment 
before pectization begins. Zirconium is very easily peptized. 
The gel is peptized by treating with a small quantity of an 
alkaline solution caustic or carbonate. Such peptized col- 
loids have in a concentrated form a high agglomerative power 
for dry powders of any kind, as, for instance, metal powders, 
giving a plastic mass which can be formed in threads, etc. These 



PATENTS 141 

are dried and heated to a temperature exceeding the melting point. 
The colloid is converted into the metallic state. If powdered 
lead be added and the plastic mass molded projectiles of high 
density and great toughness are obtained. 

1909. Kuzel (421). U. S. Patent 914,354. C. A. 3, 228. 
Filaments for electric incandescent lamps. This consists of an 

alloy of antimony with such metals as zirconium. According to 
this method, filaments are made from plastic masses consisting 
of colloidal zirconium with or without the addition of the pow- 
dered metal and with or without the addition of the colloidal 
hydroxide. Antimony is incorporated into the plastic mass in a 
colloidal or finely-divided state, or, instead of antimony, sulphur 
or oxygen compounds of antimony may be used. This plastic 
mass is brought into the desired form, dried, and heated to a white 
heat. An alloy is thus obtained with antimony the presence of 
which gives a notable increase in the electrical resistance. 

1910. Kuzel (422) . U. S. Patent 969,064. C. A. 4, 2908. 

A process for manufacturing articles with the use of colloids. 
A pasty colloid, preferably a peptized colloid, of lead or pul- 
verulent lead to which finely-divided zirconium has been added 
is brought to the desired consistency and molded under high pres- 
sure. The articles are then dried and gradually raised to a tem- 
perature below the melting point of the ingredients in the absence 
of active gases. 
1910. Kuzel (423). U. S. Patent 969,109. C. A. 4, 2909. 

Solder for electrically connecting filaments of electrical incan- 
descent lamps. The carbide of aluminum, to which may be added 
the carbide of zirconium to raise the melting temperature, is used. 
1914. Kuzel and Wedekind (424). U. S. Patent 1,088,909. C. A. 

8, 1408. 

Preparation of pure zirconium. Mix Zr0 2 and finely divided 
calcium. Enclose in a steel bomb and exhaust. Heat with a 
strong flame till reaction begins, then heat of reaction is suffi- 
cient. Cool gradually, finally in ice water. Treat contents with 
water, then dilute acid, to remove CaO. Grind, wash, and dry 
residue. To drive off gases completely, heat in vacuo to 1000. 
Zirconium about 96 p.c. pure. 
1912. Landau, Kreidl, Heller and Co. (432). Ger. Patent 294,202. 

C. A. 12, 413. 
Use as a clouding agent for enamels. Alkali zirconium com- 



142 ZIRCONIUM AND ITS COMPOUNDS 

pounds in hydrous form are used. The alkali content should lie 
between 2 and 7 p.c. The water content depends upon that of 
the alkali. The lower the alkali, the larger the amount of com- 
bined water. The water is only partially removed. 

1913. Landau, Kreidl, Heller and Co. (429). Ger. Patent 258,638. 

C. B. 1913, I, 1629. 

Use for weighting silk. This substitutes salts of zirconium for 
tin salts in weighting silk. It is carried out by the usual methods 
of practice with fixing baths. 

1914. Landau, Kreidl, Heller and Co. (431). Ger. Patents 283,504, 

281,571. C. B. 1915, I, 280. 

These refer to the use of zirconium compounds in white 
enamels. 

1909. Lesmiiller (442). Ger. Patent 231,002. Chem. Ztg. Rep. 

1911, 108. 

Use for making sound castings. Zirconium in metallic form 
is added to the metal to be cast to insure a casting free from 
imperfections. 

1910. Lesmuller (443). Ger. Patent 218,316. Chem. Ztg. Rep. 

1910, 91. 

Use as a clouding agent. Borax or boron trioxide melted with 
zirconia gives a colorless glass if enough of the borax is used. 
The solution of the zirconia is aided by the presence of silica. 
If cooled under steam or acid vapors, cloudings caused by the 
separation of double compounds with B 2 3 are given. By slow 
cooling the separation is avoided and amorphous, homogeneous 
masses are obtained. The enamel is stable towards acids and 
alkalies. 
1914. Leuchs (444). Ger. Patent 285,344. C. A. 10, 375. 

This refers to the purifying of zirconia. Add H 2 S0 4 to a solu- 
tion of the chloride in the proportion 7Zr0 2 :4H 2 S0 4 and boil. 
Without applying pressure a readily filtered, crystalline, iron- 
free precipitate of basic zirconyl sulphate (ZrO 2 .3S0 3 .14H 2 0) is 
obtained. Precipitate with ammonia or caustic alkali, dry, and 
pulverize. The product is especially suitable for enamels. 
1918. Loveman (454). U. S. Patent 1,261,948. 

This is a process for purifying zirconia ores. Alumina and 
silica are removed by fusion with Na 2 C0 3 added in a ratio greater 
than 1 : 6 and leaching out the aluminate and silicate. The 
residue is then treated with dilute HC1, washed, and ignited. 



PATENTS 143 

1896. Muller-Jacobs (513). U. S. Patent 558,197. Ber. d. chem. 

Ges. 29, d, 448. 

A method for manufacturing tannate of zirconium. This con- 
sists in dissolving a salt of zirconium in boiling water and slowly 
adding a saturated solution of tannic acid heated to boiling, wash- 
ing and filtering the precipitate, and drying at a suitable tem- 
perature not exceeding 100. This may be used to decolorize 
solutions, to make lac dyes, to prevent or retard fermentation, 
and as an antiseptic. 
1914. North (524). Ger. Patent 288,969. C. A. 10, 2461. 

A method of recovering the valuable constituents in zirconium 
ores. The ore is added to molten, high-carbon iron to the com- 
plete saturation of the metal and the metallic solvent, then re- 
moved by dissolving in acids or burning off. In using ground 
ore (Zr0 2 85.7 p.c., Si0 2 7.4 p.c., Fe 2 3 4.1 p.c., and Ti0 2 0.6 p.c.) 
the residual mass has a very high melting point and approaches 
zirconium in properties. 
1920. North and Loosli (525). Brit. Patent 155,299. C. A. 15, 

1108. 

Preparation of zirconium. Zirconium ore or oxide is reduced 
by mixing it with the theoretical amount of carbon and heating 
the mixture under increased pressure in an electric furnace. The 
current may pass through the charge itself or a conductive carbon 
core may be used. 
1918. Norton Co. (527). Brit. Patents 113,958 and 113,959. C. A. 

12, 1442. 

Production of an abrasive. A crystalline product is obtained 
by fusing alumina and zirconia in an electric furnace, the pro- 
portion of zirconia ranging up to equi-molecular. Bauxite is 
calcined and mixed with zirconia. If desired, a small percentage 
of coal is added to reduce the iron oxide and silica. Powdered 
zircon may be used. The product, together with a binding ma- 
terial, may be formed into wheels, etc. 
1920. Petinot (541). U. S. Patent 1,335,982. C. A. 14, 1519. 

Alloy of zirconium and lead. This is formed by melting a 
mixture of Zr0 2 and CaO in such proportions as to prepare 
CaZrO 3 , adding sufficient carbon to reduce the Zr0 2 to Zr and 
to form CaC 2 , and then charging the resulting material into 
molten Pb. 



144 ZIRCONIUM AND ITS COMPOUNDS 

1920. Petinot (542). U. S. Patent 1,335,983. C. A. 14, 1920. 

Ferro-alloys containing zirconium carbide. These are formed 
by smelting a mixture of Zr ore, Fe, and C and rapidly cooling 
to prevent the formation of graphite. They contain zirconium 
carbide or a double carbide of Zr and Fe. 

1919. Pugh (570). U. S. Patent 1,316,107. Chem. Met. Eng. 21, 

742. 

A process for preparing basic zirconyl sulphate. Sulphuric 
acid is added to an acid solution of zirconyl chloride in the 
proportion 3H 2 S0 4 : 5Zr0 2 and heated. The product is 
5Zr0 2 .3S0 3 .13H 2 0. 

1920. Rare Metals Reduction Co. (582). Brit. Patent 138,348. 

C. A. 14, 1643. 

Alloys for lamp filaments, electrodes, etc. These non-corrod- 
ing alloys include Zr and Fe Zr 40-90 p.c. or as low as 8.43 
p.c. Ti, Al, Nb, Ta may be added and Fe replaced by Ni, Co, 
or Mn. The alloys are made by reduction of the metals, pref- 
erably in the presence of a titanium compound. All may be used 
in the reduction. 
1915. Rietz (591). Brit. Patent 4,457. Soc. Chem. Ind. 35, 532. 

Fireproofing and weighting silk by a uniform impregnation with 
the hydrogel of zirconium hydroxide. The material is steeped 
in a solution of a zirconium salt, e.g., zirconium acetonitrate 
(obtained by evaporating a solution of zirconium nitrate and 
acetic acid). A neutral salt is added (as MgSOJ, the product 
drained and heated for 45 minutes at 60-70. For fireproofing, 
the impregnated material is treated with dilute phosphoric acid, 
or precipitated zirconium phosphate is dissolved in a concen- 
trated solution of oxalic acid and the material impregnated, with 
or without subsequent treatment with a neutral salt, and heated 
at 70. 

1921. Rietz (592). U. S. Patent 1,366,101. C. A. 15, 934. 
Clouding glass, enamels, and glazes. Fluorides are used in 

conjunction with compounds of Zr. As example a frit consisted 
of Na 2 C0 3 , feldspar, quartz, native Zr0 2 , and sodium silico- 
fluoride. The fluorides are used in larger proportions than 
hitherto. The batches must contain a large proportion of Si0 2 . 
1919. Rosenhain and Rodd (606). U. S. Patent 1,307,881. C. A. 

18, 2261. 
Production of a basic zirconium sulphate. This is prepared 



PATENTS 145 

by adding an alkali, as NH 4 OH to a solution containing zirconium 
sulphate and hydrochloric acid until so far neutralized that a 
permanent precipitate begins to form and then allowing the pre- 
cipitation to proceed without further addition of alkali. 
1919. Rosenhain and Rodd (607). U. S. Patent 1,307,882. C. A. 

13, 2261. 

Production of a basic zirconium chloride. This compound has 
the composition Zr 5 8 Cl 4 .22H 2 and is soluble in water. Dis- 
solve wet Zr(OH) 4 in equal volumes of HC1 and H 2 (D. 1.15) ; 
concentrate the solution until crystals form on cooling. These 
are mixtures of the above with ZrOCl 2 . 8H 2 0. On recrystallizing 
from HC1 (D. 1.08) the basic chloride crystallizes alone. 
1919. Rosenhain and Rodd (608). U. S. Patent 1,307,883. C. A. 

13, 2261. 

Production of a basic zirconium sulphate. This salt has the 
composition 5Zr0 2 . 2S0 3 . 14H 2 and is sparingly soluble in water. 
It is formed from the basic chloride, Zr 5 8 Cl 4 .22H 2 0, by dis- 
solving in thirty times its weight of water and adding H 2 S0 4 ac- 
cording to the equation 

Zr 5 8 Cl 4 + 2H 2 S0 4 = 5Zr0 2 .2S0 3 + 4HC1. 

1904. Ruff (622). Ger. Patent 286,054. C. A. 10, 956. 
Preparation of zirconium carbide. The oxide is mixed with 

coal or placed in a carbonizing atmosphere and heated. For 
example, 1 k. crude or purified Zr0 2 is mixed with 300 g. coal 
and heated in a graphite crucible. At about 1900 a copious 
evolution of gas sets in and continues on increase of temperature. 
It is raised to 2100. There is direct production of a fine pow- 
der. The fineness is determined by the height of the final tem- 
perature. 

1905. Sander (632). Ger. Patents 133,701, 137,568, and 137,569. 

C. B. 1905, I, 1290. 

Zirconium incandescent electric lamps. The filaments are 
made of zirconium hydride and nitride or of zirconium carbide 
(90 parts) and rhodium (or the corresponding amount of oxide) 
(10 parts), which are worked into form by suitable methods. 
These filaments are very hard, not brittle, and have a metallic 
appearance. They conduct electricity as the metal does. The 
lamps are evacuated or filled with hydrogen. The normal effi- 
ciency in use is 2 watts per candle power. They burn 700-100Q 
hours and give only a slight deposit in the lamps. 



146 ZIRCONIUM AND ITS COMPOUNDS 

1906. Sander (633). Ger. Patents 147,316 and 154,691. 

These refer to the production of zirconium from the hydride 
and nitride. 
1920. Sicard (656). U. S. Patent 1,335,991. C. A. 14, 1519. 

Alloy of iron, zirconium, and titanium. This is formed by 
mixing baddeleyite, rutile, and scrap iron with carbon in sufficient 
quantity not only to reduce the oxides but to combine the metals 
to form a complex carbide which is smelted in an electric furnace. 
The alloy may contain Zr 35-40 p.c., Ti 4-5 p.c., C 4-8 p.c., and 
Fe 57-47 p.c., which may be used in forming zirconium steel. 
1920. Sicard (657). U. S. Patent 1,335,992. C. A. 14, 1519. 

Zirconium steel. This ferro-alloy is formed by adding the 
alloy of Fe, Zr, Ti, and C to molten steel. The Ti prevents oxi- 
dation of the Zr. 

1913. Stern (678). Ger. Patent 261,142. C. B. 1913, II, 187. 

Use for weighting silk. The fibers are impregnated with solu- 
tions of tungsten and molybdenum salts and then treated with a 
solution of a zirconium salt. Precipitate forms on the fiber. The 
baths may be reversed. 

1914. Stern (679). Ger. Patent 276,423. Z. angewand. Chem. 27, 

500. 

This refers to the use of zirconia in gas mantles. 
1919. Wade (755). Brit. Patent 153,113. C. A. 15, 930. 

A new basic sulphate of zirconium of the composition 
5Zr0 2 .3S0 3 .13H 2 0, free from Fe, Ti, and Si, is obtained by add- 
ing H 2 S0 4 in the requisite quantity to a solution of zirconyl 
chloride containing free acid, preferably HC1. The basic zirconyl 
sulphate is precipitated on heating. 
1910. Weintraub (796) . Brit. Patent 25,033. C. A. 6, 1406. 

Preparation of pure zirconium. The metal may be prepared 
by the action of hydrogen upon zirconium halides at the tem- 
perature of the electric arc. 
1919. Weintraub (797). U. S. Patent 1,306,568. C. A. 13, 2113. 

Preparation of pure zirconium. Halogen compounds of zir- 
conium, as the chloride, are reduced by the action of hydrogen 
mixed with the vapor of sodium or potassium in a reaction vessel 
heated externally by a gas burner and internally by an incan- 
descent filament. The temperature is high enough to volatilize 
the NaCl formed but not to volatilize the metal about 1600 
abs. The gas stream may be omitted and the reduction take 



PATENTS 147 

place in a vacuum. The metal prepared in this way contains 
only 0.001 p.c. of impurities. 

1910. Weiss (798). Ger. Patent 230,757. C. B. 1911, 320, or II, 

524 (?). 

This refers to the use of zirconia as an abrasive and polishing 
agent. 

1910. Weiss (799). Ger. Patent 235,495. Chem. Ztg. Rep. 35, 320. 
The preparation of white pigment and lacs. Starting with 
most of the compounds of zirconium (oxide, silicate, carbonate, 
phosphate, sulphite) a pure white pigment may be obtained on 
ignition. This is stable at high temperatures and most resistant 
to chemical action. It is not attacked by acid or alkali and 
not changed by hydrogen sulphide. It is not poisonous. It is 
worked up with the usual vehicles. 

1910. Weiss (800). U. S. Patent 982,326. Chem. Ztg. Rep. 36, 320. 
Production of ferro-zirconium. 

1911. Weiss (803). Ger. Patent 237,624. Chem. Ztg. Rep. 35, 1262. 
This refers to the use of zirconia as an inert powder for 

medicinal purposes. 
1885. Welsbach (810). Ger. Patent 39,162. Ber. d. chem. Ges. 20, 

Ref. 406. 

The use of zirconia in gas mantles. This use is along with 
oxides of the rare earths, giving a white light. The making of 
the mantles is described. 
1889. Welsbach (811). U. S. Patent 409,653. Chem. Ztg. 13 (2), 

1192. 

The preparation of zirconium nitrate. Zircon is pulverized, 
washed, digested with concentrated HC1 to remove iron, mixed 
with twice its weight of Na 2 C0 3 , and heated to a white heat. The 
melt is leached with water and the insoluble residue treated with 
excess of H 2 S0 4 , which excess is later driven off. The zirconium 
sulphate is dissolved in water, precipitated by NH 4 OH, and the 
zirconium hydroxide dissolved in nitric acid. This nitrate may 
be used in gas mantles. 
1905. Wolfram Lampen Ges. (822). Ger. Patent 200,300. C. A. 

2, 2909. 

A means of overcoming the brittleness of tungsten filaments. 
Zirconium is added to tungsten and the filaments are formed with 
the addition of tin chloride-cellulose or glacial acetic collodion, 



148 ZIRCONIUM AND ITS COMPOUNDS 

denitrated, sintered, decarbonized by heating in hydrogen, and 
heated to incandescence by electric current. 
1907. Zerning (830). Brit. Patent 20,233. Soc. Chem. Ind. 27, 

1197. 

Lamp filaments. Heat zirconia with zinc dust in a hydrogen 
atmosphere. Then treat with acid to remove the zinc oxide and 
wash with water, alcohol, and ether, successively. The zirconium 
retains or combines with the hydrogen. Mix this product with 
12-16 p.c. of a suitable binder, as nitro-cellulose in anyl acetate 
to which some castor oil has been added, and use to coat the 
inside of iron vessels in which lamp filaments are heated. 



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649. 1888, Schmidt and Haensch, 667. 

Emissive power of Linne- 
mann's light. Ann. Phys. 
Beibl. 12, 244. 668. 

650. 1919, Scriyenor, Occurrence with 

cassiterite and pleiochroism. 
Geol. Mag. 6, 123; C. A. 14, 669. 
715. 

651. 1855, Schrotter, Occurrence in 670. 

zoisite. /. prakt. Chem. 64, 
316. 

652. 1911, Schroeder, Separation and 671. 

determination by cupferron. 
Z. anorg. Chem. 72, 95. 

653. 1919, Schwarz and Deisler, Non- 672. 

existence of the monoxide. 

Ber. 52, 1896. 673. 

654. 1920, Searle, Zirconia bricks for 

gas generators. Chem. Age 674. 

(London) 2, 684; ibid., 8, 123; 

C. A. 14, 3141. 675. 

655. 1913, Seger and Crawer, Zircon 

glass. Chem. Ztg. 87, 206. 



1920, Sicard, Zirconium iron and 
titanium alloy. U. S. Pat. 
1,335,991; C. A. 14, 1519. 

1920, Sicard, Zirconium steel. U. 
S. Pat. 1,335,992; C. A. 14, 
1519. 

1920, Singer, Zirconia in pior- 
celains. Dingler's Polyt. J. 9, 
96; C. A. .74,2845. 

1850, Sjogren, Occurrence in cata- 
pleiite. Ann. Phys. 79, 300. 

1852, Sjogren, Peculiarity of zir- 
conia from catapleiite. Ann. 
Phys. (3) 3, 465. 

1903, Smith, Action of sodium 
carbonate on zirconia. Z. 
anorg. Chem. 27, 336. 

1914, Smith, Varieties of zirkelite 
from Ceylon. Min. Mag. 16, 
309; Chem. Zentr. 1914, I, 
1284. 

1895, Smith and Harris, Action 
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17, 654. 

1920, Smith and Jones, Deter- 
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Soc. W, 1764. 

1896, Sohren, Light emission in 
zirconia mantles. J. Soc. Chem. 
Ind. 15, 701. 

1919, Somers, Zircon in clays of 
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Acad. Sci. 9, 113; C. A. 13, 
1753. 

1869, Sorby, New element, jargo- 
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19, 121. 

1869, Sorby, Spectrum of zirco- 
nium and uranium. Chem. 
News 19, 142, 181. 

1869, Sorby, Further work on 
jargonium. Chem. News 20, 7. 

1880, Soret, Ultraviolet absorp- 
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(3) 4, 261 ; Jahresber. 1880, 214. 

1899, Spezia, Color of zircon. 
Accad. real. Torino. 34', Chem. 
Zentr. 1900, I, 198. 

1828, Sprengel, Presence in 
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1904, Stabler and Denk, Zirco- 
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1905, Stabler and Denk, Halogen 
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1919, Staley, Use in enameled 
cast-iron ware. U. S. Bur. 
Stand. Tech. Paper 1$. 



166 



ZIRCONIUM AND ITS COMPOUNDS 



676. 1901, Steele, Position in the peri- 

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245. 697. 

677. 1918, Steiger, Determination as 

phosphate. J. Wash. Acad. Sci. 

8, 657; C. A. 13, 290. 698. 

678. 1913, Stern, Use for weighting 

silk. Ger. Pat. 261,142; Chem. 
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679. 1914, Stern, Use for gas mantles. 699. 

Ger. Pat. 276,423; Z. angew. 
Chem. 27, 500. 

680. 1903, Stevanovic, Possibility of 

unknown element accompany- 700. 
ing zirconium. Z. Kryst. 37, 
247. 

681. 1903, Stevanovic, Color of zircon. 701. 

Z. Kryst. 37, 622. 

682. 1895, St. John, Light emission at 

high temperatures. Ann. Phys. 702. 
66, 433. 

683. 1884, Stolba, Opening up of zir- 703. 

cons. Chem. News 49, 174. 

684. 1869, Streit and Franz, Separa- 

tion from titanium. J. prakt. 704. 
Chem. 108, 75. 

685. 1822, Stromeyer, Occurrence in 

eudialite. Jahresber. 1, 40. 705. 

686. 1859, Stromeyer, Precipitation by 

thiosulfate. Ann. 113, 127. 

687. 1904, Strutt, Argon and helium 706. 

in malacone. Proc. Roy. Soc. 
78 A, 193. 

688. 1907, Strutt, Radioactivity of zir- 707. 

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152. 

689. 1909, Strutt, Radioactivity of 

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298. 

690. 1914, Strutt, Color of zircons and 

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691. 1901, Sustchinsky, Zircons in the 

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Nat. St. Petersburg 29, 5; 
Chem. Zentr. 1901, II, 225. 

692. 1845, Svanberg, A new earth, no- 

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65, 317. 

693. 1848, Svanberg, Density of zir- 

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694. 1907, Szilard, Colloidal hydrox- 

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Chem. Zentr. 1908, I, 607. 

695. 1907, Szilard, Colloidal hydrox- 714. 

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Chem. Zentr. 1908, I, 797. 

696. 1905, Tacconi, Crystal forms of 715. 

zircons. Atti Accad. Lincei (5) 



14, 88; Chem. Zentr. 1905, II, 
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1905, Tammann, Action of sili- 
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1907, Tanatar and Kurovsky, 
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1910, Tanatar and Kurovsky, 
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1869, Taylor and Harrison, Zir- 
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1869, Thalen, Wave lengths of 
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1912, Thomas, Zircon glass. 
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1920, Thompson, Analysis of zir- 
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1910, Thomson-Houston, Reduc- 
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1914, Thornton and Hayden, Sep- 
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1907, Thoulet, Zircon from sea 
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1914, Tiede and Birnbraner, Be- 
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1921, Tiede and Jenisch, Zirco- 
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1896, Traube, Treatment of zir- 
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1919, Travers, Analysis of zir- 
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1798, Trommsdorff, Efforts to re- 
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1833, Trommsdorff, Valerianate. 
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1865, Troost, Zirconium. Compt. 
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1893, Troost, Preparation of zir- 
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1893, Troost, Extraction of zir- 
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BIBLIOGRAPHY 



167 



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168 



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1903, Wedekind, Colloidal zirco- 
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1908, Wedekind, Colloidal zirco- 
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1908, Wedekind, Iron-free zir- 
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1910, Wedekind, Colloidal zirco- 
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1911, Wedekind, Conduct of zir- 
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1912, Wedekind, Metallic zirco- 
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1914,' Wedekind and Rheinboldt, 
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795. 1887, Weibull, Crystalline forms 

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798. 1910, Weiss, Zirconia as polish- 

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802. 1910, Weiss, Zirconia for cloud- 

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SUBJECT INDEX 



Acetates, 110, 111. 

basic zirconyl acetates, 111. 

normal acetate hydrolysis, 111. 

normal zirconium acetate, 111. 

zirconyl acetate, 111. 
Acetylacetonate, 115. 
Adelfolith, 20. 
Adsorption compounds, 32. 
Alvite, 20, 21. 
Amide, 46, 47. 
Analytical methods, 120, 125. 

qualitative, 120, 121. 

quantitative, 121, 122. 

separations, 123, 124, 125. 
Anderbergite, 20, 21. 
Antimonate, pyroantimonate, 93, 94. 
Applications, technical, 125-132. 

abrasives, 132. 

alloys, 128-129. 

chlorinating agent, 132. 

clouding agent, 130. 

colloidal uses, 131. 

combustion tubes, 130. 

crucibles, 130. 

electrodes, 129. 

enamels, 130. 

filaments, 127. 

furnace lining, 129, 130. 

gas mantles, 127. 

glass, 131. 

insulating materials, 129. 

jewels, 126. 

medicinal, 131. 

mordanting, 131. 

oxy-hydrogen light, 126, 127. 

pigment, 131. 

reducing agent, 128. 

refractories, 130. 

scavenger, 129. 

weighting filter, 131. 
Arrhenite, 20, 21. 
Arsenates, 93. 
Astrophyllite, 20, 21. 
Auerbachite, 20, 21. 
Azide, 46. 

Baddeleyite, 20, 98. 

Beccarite, 20, 21. 

Benzoate, basic zirconyl benzoates, 114. 



Bibliography, 149-169. 
Boride, 49, 50. 



Brazilite, 20, 21. 

Bromides, addition compounds, 72. 

basic zirconyl bromides, 73. 

normal zirconium tetrabromide, 72. 

preparation of, 72. 

properties of, 72. 

zirconyl bromide, 72. 

Carbide, zirconium carbide, 30, 47. 
Carbonates, absorption of carbon dioxide 
by hydroxide, 110. 

basic zirconyl carbonates, 110. 

precipitation by alkaline carbonates, 



Catapleiite, 20, 21, 103. 

Chalkolamprite, 20, 21. 

Chlorate, basic zirconyl chlorate, 71 ; 

normal zirconium chlorate, 71. 
Chromate, basic zirconyl chromate, 94. 
Citrate, ammonium zirconium citrate. 

Ill, 112. 

Cyanides, zirconyl cyanides, 116. 
Cyrtolite, 20, 21. 

Discovery of the element, 15. 
Distribution of ores and minerals, 17, 18. 

Elpidite, 20, 21, 103. 
Erdmannite, 20, 21. 
Eudialyte, 20, 21. 
Euxenerde, 20, 21. 

Fergusonite, 20, 21. 

Ferricyanide, zirconyl ferricyanide, 116. 
Ferrocyanide, zirconyl ferrocyanide, 116. 
Fluorides, normal zirconium fluoride, 53. 
preparation of, 53. 
properties of, 54. 

constitution of hydrate, 54. 

double salts (vid. fluozirconates), 55. 

loss in analysis, 54. 

zirconyl fluoride, 54. 
Fluozirconates, 55. 

ammonium fluozirconate, 56, 57. 

barium fluozirconate, 61. 

cadmium fluozirconate, 61. 

caesium fluozirconate, 58, 59. 

calcium fluozirconate, 60. 

copper fluozirconate, 60. 

lead fluozirconate, 61. 

lithium fluozirconate, 55, 56. 

magnesium fluozirconate, 62. 

manganese fluozirconate, 62. 

nickel fluozirconate, 62. 

nickel and potassium fluozirconate, 62. 

potassium fluozirconate, 57, 58. 

rubidium fluozirconate, 58. 

silicon (zirconium sili co-fluoride ), 63. 

sodium fluozirconate, 56. 

strontium fluozirconate, 60. 

thallium fluozirconate, 63. 

zinc fluozirconate, 61. 
Formates, normal zirconium formate, 110. 

zirconyl formate, 110. 
Formulas for basic zirconyl salts, 33. 

Hiortdahlite, 20, 21. 

History of the element, 15, 16. 

Hyacinth, 17, 18. 

Hydride, zirconium hydride, 34, 35. 

Hypophosphite, 92. 

Jacinth, 17. 
Jacupirangite, 20. 
Jargon, 17. 
Jargonium, 16. 

Kochelite, 20, 21. 
Lovenite, 21, 103. 



171 



172 



SUBJECT INDEX 



Malacone, 20, 21. 
Mengite, 97. 
Mqlybdates, 95, 96. 
Monoxide, 35. 
Mosandrite, 21. 

Nitrates, addition compounds with zir- 

conyl nitrate, 89. 
basic zirconyl nitrates, 88. 
dialysis of basic nitrates, 89. 
existence of normal zirconium nitrate, 

87. 

hydrates of zirconyl nitrate, 87. 
hydrolysis of zirconyl nitrate, 88, 89. 

zirconyl nitrate, 87. 
Nitrides, 30, 45, 46, 47. 
Noria, 16. 

Occurrence of zirconium compounds, 16- 

21. 

Olivieraite, 21. 
Ores, distribution of, 17, 18. 
Organic acids, 110-113. 
Organic bases and tetrahalides, 114-119. 

addition compounds formed, 117-118. 

precipitates formed, 119. 
Oxalates, ammonium zirconium oxalate, 
112, 113. 

basic zirconyl oxalates, 112. 

solubility of hydroxide in oxalic acid, 
112. 

zirconyl oxalate, 112. 
Oxide (vid zirconia). 
Oxysulphide, 49. 

Patents, 133-148. 

abrasive, 143. 

abrasive and polishing agent, 147. 

alloy for high melting point and 
ductility, 139. 

alloy Zr, Fe, Si, Cr, Ni, Mn, 135. 

alloy Zr, Fe, Ti, 146. 

alloy Zr, Nb, Ta, 137. 

alloy Zr, Ni, 134. 

alloy Zr, Ni, Al, Si, 135. 

alloy Zr, Ni, Al, Si, W, Fe, 135. 

alloy Zr, Ni or Co, Cr, 135. 

alloy Zr, Pb, 143. 

alloy Zr, Sb, 141. 

alloys for filaments, electrodes, etc., 
144. 

alumino-thermic reduction, 134. 

basic zirconyl chloride, 145. 

basic zirconyl sulphate, 144, 145, 146. 

basic zirconyl sulphate and chloride, 
137. 

brittleness of tungsten filaments re- 
moved by Zr, 147. 

carbide preparation, 145. 

castings, 142. 

chemical application of zirconia, 138. 

clouding agent for enamels, 142. 

clouding agent, 142. 

clouding glass, enamels, and glazes, 144. 

clouding composition for enamels, 136. 

colloid, use of, 141. 

colloidal zirconium, 140. 

crystallizing zircon, 138. 

cyanonitride, 133. 

drawing filaments, 139. 

enamels, 136. 

enamels, white, 142. 

ferro alloys containing carbide, 144. 

ferro-zirconium, 134, 147. 

ferro-zirconium alloys, 137. 

ferro-zirconium (steel), 146. 

filament, improvements detailed, 138. 

filament, improvements in production, 
138. 



Patents Continued. 

filament for lamps, 136, 145, 148. 

filament production, 136. 

filament solder, 141. 

fire-proofing and weighting silk, 144. 

fusion of zirconia with caustic alkalis, 

134. 

gas mantles, 146, 147. 
inert powder for medicinal use, 147. 
iron free zirconia for enamels, 138. 
iron free zirconia, detailed, 138. 
manufacture of alloys for filaments, 

140. 

metallic zirconium or its alloys, pro- 
duction, 136. 
nitrate preparation, 147. 
nitride production, 133. 
nitride purification, 134. 
opacifier for enamels, 138. 
ores in gold extraction, 139. 
peptizing coagulated zironium colloid, 

140. 
porcelain (clay, feldspar and zirconia), 

135. 
recovery of valuable constituents in 

zirconium ores. 143. 
refractory of zirconia and alumina, 139. 
refractory of zirconia and chromite, 

139 

refractory vessels, 139, 140. 
separation from iron, 133. 
separation as pyrophosphate, 134. 
separation from rare earths by elec- 
trolysis, 135. 
silicide, oxide and salts, preparation, 

139. 

utensils of zirconia, 133. 
weighting silk, 142, 146. 
white pigment and lacs, 147. 
zirconia ores, purification, 143. 
zirconia, preparation from ore, 137. 
zirconia, pure, from zirkite, 138. 
zirconia purifying, 142. 
' zirconium, pure, production, 141, 146. 
zirconium, preparation, 143. 
zirconium preparation from hydride or 

nitride, 146. 
Pentoxide, 44. 
Perchlorates, acid zirconyl perchlorate, 

71. 

basic zirconyl perchlorate, 71. 
Periodate, basic zirconyl periodate, 75. 
Perzirconates, lithium perzirconate, 107. 
potassium perzirconate, 107. 
sodium perzirconate, 107. 
Phosphates, basic zirconyl phosphates, 91. 

double salts with alkalis, 92. 

double salts with sodium, 92, 93. 
hypophosphite, 92. 
pyrophosphate, 90. 
solubility of hydroxide in phosphoric 

acid, 89. 

' subphosphate, 91. 
Phosphide, 51, 52. 
Polymignite, 21, 97. 
Pyrochlor, 21. 
Pyrophosphate, zirconium pyrophosphate, 

92. 
Pyroracemate (propanonate), 115. 

Rosenbuschite, 23. 

Salicylates, basic zirconyl salicylates, 115. 
Selenates, basic zirconyl selenates, 86. 
Selenite, basic zirconyl selenites, 85, 86. 

normal zirconium sele.nite, 85. 
Silicates, artificial, 103. 

calcium zirconium silicate, 104. 



SUBJECT INDEX 



173 



Silicates Con tinued. 

lead-zirconium silicate, 104. 

potassium-zirconium silicate, 104. 

sodium-zirconium silicate, 103, 104. 

vid zircon. 
Silicide, 50, 51. 
Silico-fluoride, 63. 
Subphosphate, 91. 
Sulpharsenate, 93. 
Sulphates, acid zirconium sulphate, 78. 

acid zirconyl sulphate, 81. 

basic zirconyl sulphate, 80, 81, 82. 

double salts with zirconium sulphate, 
80. 

double salts with zirconyl sulphate, 83. 

hydrolysis of zirconium sulphate, 78. 

normal zirconium sulphate, 77. 

preparation of zirconium sulphate, 77. 

properties of zirconium sulphate, 77. 

zirconyl sulphate, 81. 
Sulphite, basic zirconyl sulphite, 76. 

normal zirconium sulphite, 76. 

Tachyaphaltite, 21. 
Tantalite, 21. 

Tartrates, basic zirconyl tartrate, 113. 
zirconyl-ammonium tartrate, 113. 
zirconyl-potassium tartrate, 113. 
solubility of hydroxide in ammonium 

tartrate, 113. 
solubility of hydroxide in tartaric acid, 

113. 

Tellurate, zirconyl tellurate, 86. 
Tellurite, zirconyl tellurite, 86. 
Thiocyanate, zirconium thiocyanate, 116. 
organic double compounds with zir- 
conium thiocyanate, 116. 
Titanates, natural occurring titanates, 97. 

zirconvl titanates, 97. 
Trioxide^ 44, 45. 

Tungstates, ammonium zirconyl tung- 
states, 95. 

basic zirconyl tungstates, 94. 
potassium zirconyl tungstates, 95. 

Uhligite, 21. 

Valerianate, 115. 
Vanadate compound, 96. 

Wohlerfte, 21, 103. 

Zircon, altered, 98. 
analyses, 98. 
artificial, 102. 
chemical behavior, 99. 
color, 19. 

composition, 17. 18, 98. 
crystal form, 97. 
luminescence, 99-102. 
melting point, 99. 
minerals, 20. 



Zircon Continued. 

occurrence, 17, 18. 

specific gravity, 99. 

types, 21. 
Zirconates, 33. 

barium zirconate, 108, 109. 

calcium zirconate, 108. 

formation of zirconates, 104. 

lithium zirconate, 107. 

magnesium zirconate, 108. 

perzirconates, 107. 

potassium zirconate, 107. 

sodium zirconate, 106. 

strontium zirconate, 108. 
Zirconia, boiling point, 39. 

chemical conduct, 39, 40. 

coefficient of expansion, 39. 

conductivity for electricity, 39. 

conductivity for heat, 39. 

crystalline form, 39. 

crystallization, 38. 

heat of formation, 39. 

light emission, 39. 

melting point, 39. 

native, 36. 

occurrence, 36. 

preparation from zircons, 37, 38. 

porosity, 39. 

purification of native, 36, 37. 

reflecting power, 39. 

specific gravity, 39. 

specific heat, 39. 

volatilization, 39. 
Zirconium, adsorption compounds, 32. 

aluminum compounds, 23. 

amorphous, 23, 26. 

atomic number, 31. 

atomic weight, 31. 

cations, 32. 

chemical behavior, 30. 

colloidal metal, 26. 

electrical properties, 28. 

hydroxide, 40. 

hydroxide dehydration, 40, 41. 

hydroxide solubility, 41, 42. 

melting point, 27. 

monoxide, 35. 

normal salts, 32. 

optical properties, 28. 

oxide vid, zirconia. 

pentoxide, 44. 

preparation, 22, 23, 24. 

specific gravity, 27, 28. 

spectrum, 28, 29. 

trioxide, 44, 45. 

values, 32, 33. 
Zirconsulphuric acid, 79. 
Zirconyl radical, 32, 33. 
dehydration, 41. 
formation, 43. 

ionic migration, 105. 
solubility, 41, 42. 

zirconyl hydroxide, 40, 41, 105. 
Zirkelite, 19, 20, 21, 99. 



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